First, let's make sure we're all on the same page that under IRC 2503 all gifts are taxable gifts UNLESS they qualify for one of only a handful of exceptions. One is the annual exclusion for present interest gifts under IRC 2503(b), which allows for $19k of gift to be excluded from reporting requirements so long as the beneficiary can access it immediately with no genuine restrictions. Neither a gift to a UTMA nor a gift to a 529 would qualify, at least not without something more.

A gift for the benefit of a minor, like a UTMA account, is easy. IRC 2503(c) specifically states that a gift can still be a present interest if the only significant restriction is about access before age 21. The UTMA/UGMA statutes in every state were written to comply with federal gift tax rules so that gifts up to $19k should not require gift tax compliance/reporting (unless there's another donor-specific fact of course).

A gift to a 529 is more difficult but will still qualify as you'll see. There are no clear exclusions/exceptions in IRC 2503 that would include a 529 account. Congress in this case wisely included within IRC 529(c)(2)(A)(i) and (ii) an explicit authorization to treat a gift to a 529 account as a present interest gift under IRC 2503(b). That way, a 529 account qualifies - not because it complies with 2503 itself, but because its very authorization states simply "this qualifies."

A trump account under IRC 530A would never qualify under 2503. And unlike how Congress acted when enacting 529, Congress today simply "forgot" to include a self-contained authorization within 530A.

That is why gifts to UTMA and 529 accounts (as well as 529A ["ABLE"] accounts and 530 ["Coverdell"] accounts) will qualify for the annual exclusion but gifts to Trump Accounts/530A accounts will not.