Nether Portal removes bedrock blocks

Nether portals can spawn on top of bedrock blocks which can be easily exploited to punch holes in the world (both overworld and nether).

Steps to Reproduce:

1. Mine out a hole 16x16 (not necessarily chunk aligned) down to Y -59;
2. Cover closest to the hole surface areas in water or redstone dust to make sure portal spawns at the bottom of the hole;
3. Write down coordinates of the center of the hole and divide them by 8 (X/8 and Z/8);
4. Fly away about 200 hundreds of blocks away, build a nether portal and enter it;
5. Once in the nether, go to the coordinates that you got in the step 3 and build a portal back to the overworld;
6. Destroy the portal you spawned at the bottom of the mined out hole and repeat everything again many times starting from the step 4.

Observed Results:
Portal will spawn on top of deepslate and some bedrock blocks. The 4 bottom obsidian blocks of the nether portal replace a wide variety of blocks including bedrock. You can repeat it multiple times until the portal removes all the deepslate with bedrock and eventually drills a hole to the void.

Expected Results:
Portal refuses to spawn on top of bedrock blocks and spawns in the air if it couldn't find any other non-bedrock surfaces around.