Not always.
I know addition is not the same as binary or "in the genal case". But with bit flags, it is. Unless you're working on some exotic computer that doesn't use 2's complement. That is, a computer on which BlitzMax doesn't work anyway...And as hinted by the "_BIT" suffix, the constants in question were bit flags.
Well, to be completly precise, the bit flags HAVE to be exclusive or else you'll indeed go into big troubles if you just add them rather than ORing them :) (they don't necessarily have to be have just one bit set, 15 is fine if you don't add it to an overlapping bit pattern).
And it's true they're not always exclusive (but here they are), meaning taking the habit to use the bitwise or is certainly a good idea to avoid being bitten one day. Yeah, true, so I guess "should be" was actually adequate here in the sens it would be better (when I read it as "it must be for it to work").
Jeez, I'm on a nitpick roll these days, I really need to get some holidays :/
I could slap myself. You know you're really bored when your own posts make you yawn.