This was topic in COOL TC meeting minutes: 2026-07-08. I have made a spreadsheet for testing the language behavior (attached).
LogicalTest_byCO_classic.ods (15.0 KB)
My observations:
Excel is not able to use two languages in the same document. Thus it always uses TRUE/FALSE in case its UI language is English, and WAHR/FALSCH in case its UI language is German.
The current implementation for = “ABC_” & True() in COOL does not respect the language settings in the cell style. Instead it uses the locale settings from Tools > Options.
The use of the boolean terms instead of numbers 0/1 does not work, if the operand does not come from a direct function call but from a reference.