IN operator with array doesn't always work?

Y'all

I just tried the fairly new IN operator, to see if a value is in a list of items. The list has to be in an array, it seems, at 7.3, anyhow, that %LIST() is basically hard-coded thing.

Anyhow, I have an 99-element zoned(2:0) array, segXcpt. I also have a data structure element, inCtFcr.MKTSG#, that is zoned(2:0).

blox is a count of how many elements I loaded into segXcpt.

So this statement compiles fine -
     if inCtFcr.MKTSG# in %subarr(segXcpt : 1 : blox);

The following statement gives me an RNF7421 compile error (Operands are not compatible with the type of operator) -
if not inCtFcr.MKTSG# in %subarr(segXcpt : 1 : blox);

This is identical, syntactically, to the example in the documentation -
In the following example, the IF statement is true if item is not in the array availableItems. %SUBARR is used to limit the number of array elements checked.
IF NOT item IN %SUBARR(availableItems : 1 : numAvailabeItems);

What DID work is this statement, where I used parentheses - there is no hint of the need for the parentheses, even in the 7.5 documentation, IIRC.
     if not (inCtFcr.MKTSG# in %subarr(segXcpt : 1 : blox));

It looks like the RPG parser is tying the NOT to the subfield after it and treating it all as an indicator type. Something like that.

BTW, I had tried this, which I think should be allowed, and it was a different syntax error -
     if inCtFcr.MKTSG# not in %subarr(segXcpt : 1 : blox);

So I probably need to submit a case but wanted to run it by y'all first.

Regards
Vern