Making a foam block that's easy to remove but won't float out in a capsize will be tricky.
That's another advantage of an air bag - inflated in front of the footpegs or behind the seat, it's not floating out.

Sorry but I'm not following. How would a foam block wedged or velcroed into the bow area of the forward compartment, or the stern area of the aft compartment, be any more likely to float out in a capsize than an inflatable bag tossed into the compartment and not attached to anything?

I don't really understand your question about "how would I remove the foam block" either. How do you remove a float bag, or a dry sack? You just make sure that the blocks are smaller than the hatch, and you wedge or velcro them into place and add a handle or tab to enable you to grab them and take them out. Doesn't seem like brain surgery.

But, the OP has made up his mind already on this, it seems.

Made up my mind about what? What exactly do you think I'm suggesting? That kayaks shouldn't sink even if swamped? That it's prudent to add supplemental flotation? If that's just me being crazy, then why are "flotation bags" even a thing?

I suspect that this might be one of those typical online forum scenarios where you have something in your head that you think I'm saying, and you're responding to that rather than to what I'm actually saying. To be clear - I never suggested that boats shouldn't have bulkheads. I never said that bulkheads don't provide flotation. I never said that bulkheads with proper hatch covers won't provide sufficient flotation for the scenarios people are likely to encounter.

What I did say was that a boat should not rely solely on the integrity of watertight compartments to provide positive buoyancy / prevent sinking in the case of a catastrophic failure - and, in fact, wood strip kayaks do not do so.

So I'm curious - what exactly is it in what you think I said that you're objecting to?