Able to go into swimming mode by walking in angle

When I walk with a certain orientation into a block it lets me go into swimming mode. This has happened a lot of times when going into a tree. I was able to replicate it consistently (in a different scenario) in the following videos:

 

https://youtu.be/dF7P3yM0-RA

https://youtu.be/MLUfbVLSSIg