Upon some further inspection, when looking at a connected rail, you realize that its not fully connected with a block,

How to reproduce

Start by crafting some rails, then place blocks going upwards.
Then place rails on blocks, they will connect, break all the connected rails and keep 1 only, you will realize that its not connected to the block like shown in the attached video and screenshots.

Observation: Upon further inspection/examination you can tell that the rail isn't really connected to the block.
Expectations: It should be connected to the block at all times.