No if he gives the offside instead of a pen then it “should” be a free kick. The time taken to make the decision shows Collum decided no penalty as the VAR would have taken longer if they decided it was a pen. They would then have to check the attacking phase which would have ruled it out anyway hence why you see the offside part later.
The offside hasn’t been part of the decision making here, it’s just been shown to show that even if Collum throught it was a penalty, the ref would never have been invited to view it pitchside as there was an offside in the build up anyway.
Collum is probably wrong to say it’s not a penalty, I think most of us think it is however it would never have been taken
You can then say why bother checking the attacking phase and show it if the original decision was no penalty as no foul is committed, I think they do this anyway as part of their process it just doesn’t have to be done before allowing play to continue.