Excel online not refreshing when using PBI Service dataset using an On-Prem tabular model

Setup

- a very simple SSAS tabular model ("SSASModel1") deployed on-prem.

- using PBI Desktop, create a PBIX ("Scenario1") using the "SSASModel1" as the datasource (Data source type = Analysis Services) and deploy to the PBI Service.

- in PBI Gateway, a data source ("GW SSASModel1") is setup pointing to the "SSASModel1" using Windows Auth credentials. This connects fine.

- in PBI Service, the deployed "Scenario1" dataset settings the Gateway Connection maps to the "GW SSASModel1" and connects ok:  AnalysisServices{"server":"<on-prem server>","database":"SSASModel1"}  Maps to: GW SSASModel1

- in PBI Service, the deployed "Scenario1" dataset refreshes fine and report shows expected dataset. If data in "SSASModel1" changes, is processed and the "Scenario1" dataset is refreshed... the adjusted data flows through ok.

Issue

- in Excel (client tool on-prem), use Data->Get Data -> From Power BI and select the "Scenario1" dataset from the PBI Service, add in some fields/measures and save the file.

- running this file on-prem works fine. Change the data in "SSASModel1", processing "SSASModel1", refreshing the "Scenario1" dataset and finally refreshing the Excel file adjusts the data as expected.

- when moving Excel file to Office 365, after changing the data in "SSASModel1", processing "SSASModel1" and refreshing the "Scenario1" dataset... if I now try refreshing the Excel file I receive the following error:

Note: I noticed in Excel when using Get Data -> From Power BI dataset the connection string doesn't actually reference the dataset in the PBI Service, but rather it references our on-prem server and model:

Provider=MSOLAP.8;Persist Security Info=True;Initial Catalog=SSASModel1;Data Source=<on-prem server>;MDX Compatibility=1;Safety Options=2;MDX Missing Member Mode=Error;Update Isolation Level=2

I thought the PBI Service Dataset would reside in the "cloud", hold the data there and then would be used within Excel when used a as a data source. This doesn't appear to be the case.

EDIT: I found out reason behind this incorrect thought. This dataset uses a Direct/Live mode to on-premise model, so it makes sense for the dataset to simply pass the details through to the Excel file. Datasets using Import mode store the data where the reference to the PBIS dataset is passed to the Excel file.

Can the above error be resolved? Ideally whilst still leveraging oru on-premise SSAS tabular models?

Thanks