I originally came here to report a different bug-namely, that attempting to ride a boat being continually teleported above an Ender Dragon would cause the boat to fall off, and cause any subsequent interactions by the player (such as placing blocks or opening chests/command blocks) to fail-but after performing a brief search, I concluded that this was likely a manifestation of bug MC-97513, and as such is already documented.

Whilst I was testing this bug, however, I noticed a completely separate bug: The invulnerable boats that I was summoning were still breaking upon colliding with the End's obsidian pillars. Given that the boats are supposed to be invulnerable, I am guessing this is not intended behavior.

A quick search for bugs relating to invulnerable boats brought up several bugs identical to this in the past (see MC-18995, for instance), but they have all been marked as resolved as of version 1.14 or earlier. This, however, is occurring in 1.15.2.

Steps to Reproduce:
1. In a standard Minecraft world, create a line of blocks some distance off the ground. (I will use 5 blocks as an example.)
2. Place down an always-active repeating command block with the command "execute at @p run tp @e[type=boat] ~ ~5 ~", with the second tilde being how many blocks off the ground your wall is. This will teleport all boats to be directly above your head by that number of blocks, which should end up being one block above where your line is. (If not, you can readjust your line of blocks so that is the case.)
3. Summon an invulnerable boat with the command "/summon boat ~ ~ ~ {Invulnerable:1}", which should then teleport immediately above your head. (If you wish, you may use "/data get [entity name] Invulnerable" to verify that the boat is invulnerable.)
4. Run (or walk, your velocity doesn't actually matter) underneath the original line of blocks. The invulnerable boat should "land" on the blocks and break immediately, despite being invulnerable.

What I expected to happen was...:
As mentioned above, one would expect an invulnerable boat to sit on top of the blocks in this case, similar to if one had any other entity being teleported above their head in this scenario.

What actually happened was...:
As also mentioned above, the boat breaks immediately upon contact, which one would imagine should not occur.

It should be mentioned that if the line of blocks is at the same height as the boat, the boat merely clips through as per normal. This only works if the line of blocks is one block below, which leads to me to suspect that this is the fault of the boat's FallDistance property. Since it is rapidly increasing whilst it's in midair, the boat "lands" and this value set to zero when it rubs against the top of the block, causing the boat's code to break the boat without checking to see if it is invulnerable. This is only a guess, however.

I also recorded a video below of the bug for documentation. In it, you can see the boat's FallDistance listed on the far-right sidebar. The boat has the {Invulnerable:1} NBT tag when it is summoned, and it is able to pass through the right line of blocks without a problem. However, when it attempts to travel over the left line of blocks, it immediately breaks. (Sorry for the video's poor quality-I had to shrink the game window so the recording would be under the 10MB limit.)

Hopefully this gets fixed soon. If you have any questions, please let me know.