This seems unlikely - after all, a US federal law (the Credit CARD Act of 2009) requires closed-loop (store/brand-specific) gift cards to be valid for at least 5 years after activation and some states like Florida and California don't allow them to expire at all, so for simplicity national companies don't usually let them expire at all regardless of state. But neither a 5-year expiration nor indefinite validity turns the seller into a bank or an unlicensed securities seller or otherwise puts them in jeopardy.

Naturally, service credits and gift cards are probably treated differently by the CARD Act, but service credits are still not a source of legal jeopardy in the sense you were describing of being an unauthorized participant in the regulated financial world, any more than gift cards are.

I can completely believe, however, that an approach similar to how gift cards must be handled is financially worse on the company's accounting statements than quickly expiring credits. That worse financial accounting consequence would be a completely sufficient explanation for why the company switched approaches.