Watching on-line/TV, with the help of different angles and replay, the receiver certainly looked in bounds on the catch.
The HL was really in a tough spot here. The QB was running towards his side, so he does have some responsibility there and can’t just fly down the sideline.
Now, if there were 7 officials on the field (2 side judges downfield), there would have been another set of eyes much closer to the catch/no catch.
And the BJ can’t give much help, if any on that play.