Ratfolk Swarming questions: size and "attacking"

[ErichAD]

"Swarming: Ratfolk are used to living and fighting communally, and are adept at swarming foes for their own gain and their foes' detriment. Up to two ratfolk can share the same square at the same time. If two ratfolk in the same square attack the same foe, they are considered to be flanking that foe as if they were in two opposite squares."

Do ratfolk lose their swarming ability when their size changes. Supposing a ratfolk were to be large sized through some magic, could they share each square with one other creature, or one square with one other creature. What's the ruling on a large ratfolk sharing each of it's four squares with on corner of four other large ratfolks squares.

Similarly, is their ability meaningful when tiny?

Second, since attacks can't occur simultaneously, what is the exact meaning of "attacking" here. Is threatening enough or does this require a previous attack against that specific target. Can those attacks be ranged?

[Archaeik]

RAW:
Size is not indicated, so they can still share space, even when polymorphed.

Sharing is adjudicated per square, with only 2 ratfolk able to occupy any given square. (2 Large Ratfolk could occupy the same 4 squares).

When tiny, the sharing limit is superseded(overlaps with) by the normal limit of 4 tiny creatures, but the flanking provision should work for all occupants.

Ostensibly, the attack could be ranged or magical(including targeted spells), the language does not seem to care.
As for timing and duration, I'd say ask your GM. (I'd run it as starting after the 1st attacker(including if the 2nd attacker moved into that square after their ally attacked) or after a readied action to "attack simultaneously"; and then persisting until actions changed.)

RAI:
I don't see why it should care about size per se... They innately know how to share space with each other.

Polymorphed(shape/form): possibly not RAI, it would be kind of hard for some creatures to share space, but that's exactly what ratfolk understand how to do.

Tiny: I could potentially see the interpretation being "double normal occupancy", but it's not supported anywhere.

"Attacks" likely means "melee/threatens", but I also see no major issue with it functioning as written... ranged attacks do not receive the flanking bonus (and typically provoke).