DateTimeDiff vs GetDayOfWeek in Architect expressions

I can’t seem to figure out why my Architect expression fails when comparing dates. I am trying to filter events based on the day of the week. Using DateTimeDiff seems overkill for a simple weekday check, but GetDayOfWeek returns an integer that doesn’t match my string comparisons.

Here is my current attempt: GetDayOfWeek(SystemDateTime) = 1. This evaluates to false even on Mondays. Should I be using DateTimeDiff to calculate the offset from a known Monday instead? The documentation is vague on the return type of GetDayOfWeek.