Why is a lineman downfield a penalty?

[Biscanebay12]

While SF was aloud to hold Metcalf on a throw that was inches from his hands ... Yeah no steering though, just a coincidence smh

No call for pulling Deebos leg (literally), no call for late hit out of bounds on Purdy. 1 yrd is penalty for ineligible man down field, they call it when at 2 yrds.

Please just stop crying about the refs, the Hawks didn't lose because of the refs.

Did the Rams lose because of the refs? Because it sure looked to me like that running into the kicker sure went the Hawks way.