Not necessarily, say if the defender commits a foul like if the defender cuffed Maguire around the head when Maguire is standing offside, which had nothing to do with the play. Then it's a pen.
If this wasn't the case, attackers could penalty farm by simply standing offside on the wrong side at every wide free kick, then just wait for defender to try to move through them to the ball and go down. Defender can never be sure if attacker 100% offside and would make a total mockery of set pieces. Attacker is gaining an advantage and impacting the defender 100% of the time in that scenario.
Pretty certain per the Sky referee watch that this was a mistake by VAR.
Well that's violent conduct isn't it? Which is different sort of offence, but yeah it's probably that - that tweet by IFAB isn't half confusing though!