Why use CROSSFILTER ansd ALL when it works without them

[Tojo1]

Hello,

If I change the first measure to be like the second measure I get the exact same result.
So my question is if somebody could explain any reason for having the CROSSFILTER and ALL in the first measure.

First Measure
------------
var datum = CALCULATE(max(Dim_Calendar_ArrivalDate[Date]),
CROSSFILTER(Dim_Calendar_ArrivalDate[Dim_Calendar_SK],HistoryFact_Booking[Dim_CalendarArrivalDate_SK], None))
var caltable= CALCULATETABLE(Blocked_Units, Blocked_Units[date] = datum, ALL(Dim_Calendar_ArrivalDate[Date]) )
var sumxcal = SUMX(caltable, Blocked_Units[AntalUnitsBlockade])
sumxcal return

Second measure
--------------
var datum = CALCULATE(max(Dim_Calendar_ArrivalDate[Date]))
var caltable= CALCULATETABLE(Blocked_Units, Blocked_Units[date] = datum)
var sumxcal = SUMX(caltable, Blocked_Units[AntalUnitsBlockade])
sumxcal return

Many thanks in advance

Tony Johansson