Floating rails can be created with a certain setup
This is independent of the Minecart Experiments being enabled.
Steps to reproduce:
- Build the setup as shown in the image/video.
- Place a minecart on the leftmost rail.
An ascending rail is created that does not lean against any block after the mechanism completes action.
Created Issue:
Floating rails can be created with a certain setup
This is independent of the Minecart Experiments being enabled.
Steps to reproduce:
- Build the setup as shown in the image/video.
- Place a minecart on the leftmost rail.
An ascending rail is created that does not lean against any block.
Changed Description:
This is independent of the Minecart Experiments being enabled.
Steps to reproduce:
- Build the setup as shown in the image/video.
- Place a minecart on the leftmost rail.
An ascending rail is created that does not lean against any block after the mechanism completes action.
Removed Category: (Unassigned)
Added Mojang Priority:
Low
Added Affects Versions: 1.21.1

Can confirm.
This appears to be MC-26727 or MC-123311. Would you say one of these reports adequately describes your issue?
So MC-26727 is caused by pulling the rail up with a sticky piston, whereas here the rail is pushed up with a normal piston. I think that this bug might be an instance of MC-123311, though.
This happens on Bedrock Edition as well.