When I went to the End dimension and used /setblock ~ 64 ~ portal and went into the portal, I saw I was in a block. I teleported higher and saw I was in the overworld.

Steps to reproduce

1. Build an end portal or do /setblock ~ ~ ~ end_portal
2. Do /setblock ~ ~ ~ portal

What I observed

I was in the Overworld instead of the Nether and there was no Nether portal.

What I expected

I would be in the Nether with a Nether portal.