This is a know issue ABAP Restful Application Programming Model (RAP).
The workaround is the replace the BT operator with separate LE and GE operators, but this only appears to work with a single BT, not multiples.
Coming at it from another angle, is there any way we could disable the Between and Not Between operators on the Fiori Elements / Free Style (Smart Filter) app side?
at this point the solution may be using the expressed intervals.
from 01.01.2022 to 03.01.2022.
op.1) bt '01.01.2022' '03.01.2022'-
op.2) gt 01.01.2022 and le 03.01.2022
op.3) date in ( '01.01.2022','02.01.2022','03.01.2022' ).
is it suitable?