Stop obsessing. Set the bar where it needs to be and ride your bike.

If it helps you sleep better consider that no CF seat post uses an internal plug to prevent crushing or splitting when clamped.

Stems are bored to produce round on-size holes which will not distort or crush steerers, with or without the plug inside. It's kinda like how you can't break an egg by squeezing it in your palm.

FWIW I suspect that the plug canard dates to the early days of CF steerers before stem makers realized the need to produce to tighter tolerances.

BTW Trek guarantees their stuff. If they had any concern they surely would have said so.