You know, a lot depends on what is going to go on your bench regularly.
Plus, what climate, conditions in the shop.
Mold is not even a thought here in the Desert.
My first workbench was a solid core door with legs, I put together in 1988. I'm still using it. I put nothing on it, just didn't worry about grease or oil soaking into the top.
Net result, looks like a workbench and after 23 years I still use it every day.
My folding workbench I was going to use stain or oil on it. .7 Birch plywood surface.
Well, I forgot then got a bunch of oily parts on it.
That was 14 months ago, it gets used daily. It's stained, but works fine.
Wood soaks up the oil, etc. and just kind of age cures.