Incremental Refresh with Elastic Tables and Data Detection

I have a scenario where I am trying to implement incremental refresh on an elastic table using the powerbi service and a semantic model.  I'm using the ExecuteCosmosSqlQuery endpoint, which allows me to run a NoSQL query that folds until i expand it.  The query returns a createdon and modifiedon date in the format "yyyy-MM-ddTHH:mm:ssZ".  After LOTS of research and work with copilot, i verified that i can convert my RangeStart and RangeEnd Date/Time parameters to strings and even pick up the last valid refresh timestamp with a function like this:

FormatRangeStart = DateTime.ToText(RangeStart, "yyyy-MM-ddTHH:mm:ssZ"),
FormatRangeEnd = DateTime.ToText(RangeEnd, "yyyy-MM-ddTHH:mm:ssZ"),
FormatLastRefresh = LastRefreshTimeStamp("ElasticCostCollection")

My query uses paging and cookies, and all of this works.

JSONPage = (PageCookie) =>
// Make a new record based on the JSON read of the ExecuteCosmosSQLQuery function
// the API returns one page of records. If there is another page
// then the Paging Cookie will have a value and the HasMore boolean will be true.
// If HasMore is false, then this is the last read so we set a boolean called
// LastAPICall to true
let
NewRecord =
Json.Document(
Web.Contents(
"https://" & Org & EnvironmentZone,
[
RelativePath = "api/data/v9.2/ExecuteCosmosSqlQuery(QueryText=@p1,EntityLogicalName=@p2,PageSize=5000,PagingCookie=@p3)",
Query = [
#"@p1" = "'select " &
"c.props.tms_ecostcollection_controlaccount As tms_ecostcollection_controlaccount, " &
"c.props.tms_ecostcollection_elasticplanning As tms_ecostcollection_elasticplanning, " &
"c.props.tms_ecostcollection_project, " &
"c.props.tms_ecostcollection_ratestack, " &
"c.props.tms_ecostcollection_resource, " &
"c.props.tms_ecostcollection_resultunit, " &
"c.props.tms_ecostcollection_scenario, " &
"c.props.tms_ecostcollection_workpackage, " &
"c.props.tms_elasticcostcollectiondescription, " &
"c.props.tms_elasticcostcollectioneffectivedate, " &
"c.props.tms_elasticcostcollectionelementofcost, " &
"c.props.tms_elasticcostcollectionid, " &
"c.props.tms_elasticrecordid, " &
"c.props.tms_resultunitvalue, " &
"c.props.tms_transactiontype, " &
"c.props.tms_elasticcostcollectionaccountingcode, " &
"c.props.tms_elasticcostcollection_bcr, " &
"c.props.tms_ecostcollection_replanbcr, " &
"c.props.tms_ecostcollection_status, " &
"c.props.tms_ecostcollection_statusreason, " &
"c.props.tms_ecostcollection_ratesheet, " &
"c.props.tms_ecostcollection_indirectpool, " &
"c.props.tms_elasticcostcollectionappliedpoolrate, " &
"c.props.tms_elasticcostcollection_directrate, " &
"c.props.tms_elasticcostcollectionnote, " &
"c.props.partitionid, " &
"c.props.modifiedon, " &
"c.props.createdon " &
"from c " &
"WHERE c.props.createdon >= " & """" & FormatRangeStart & """" &
" AND c.props.createdon < " & """" & FormatRangeEnd & """" &
" AND c.props.modifiedon > " & """" & FormatLastRefresh & """" &
"'",
#"@p2" = "'tms_elasticcostcollection'",
#"@p3" = "'" & PageCookie & "'"
],
Headers = [
Authorization = AuthToken
]
]
)
),
Output =
Record.AddField(
NewRecord,
"LastAPICall", not Record.Field(NewRecord, "HasMore")
)
in
Output,
// In the list generate function, we run the function to pull a page from the API, and then test
// that function. Whether it is the last page or not, we accept the record into the list
// if this read was the last page, we do not call the JSONPage function again, but simply
// create an empty record with both flags set to false so the list generate function will terminate
PageRecords = List.Generate(
() => JSONPage(""),
each _[HasMore] or _[LastAPICall],
each
if not _[LastAPICall] then
JSONPage(_[PagingCookie])
else
Record.FromList (
{false,false},
{"HasMore","LastAPICall"}
)
),

It's not possible to convert the modifiedon date to a date/time field prior to the break in query folding, because the expansion of the list records to access columns breaks folding.  Copilot indicated that I should be able to add the last refresh date check in the where clause of the query (while it's still folding) and that should work, with the powerbi service retaining the records that didn't change (where the modified on date was prior to the last refresh timestamp). 

What happens:  My query seems to correctly honor the  partitions with the Range parameters, but if I run the refresh a second time, all of the records that filter out by the modified on date disappear - the service is not retaining previously loaded records in the incremental refresh period.  Does anyone know a way to actually use data detection on a field that represents a date/time value but returns as a string?  Any help would be greatly appreciated!