If it was an error on the part of the linesman and thought he was offside, it's a better process than him not being sure, not flagging, and things developing without ever checking things.
My understanding of VAR and offside is that the one thing they want to avoid is an incorrect offside flag that stops the game and prevents a goal scoring opportunity, only to find out after everyone has stopped, that it was actually onside.
So the process for an assistant should be that if they are unsure, they do not raise their flag. If a goal is scored, VAR can deal with that. If a goal is not scored in what ever the amount of phases of play it is, the assistant should then fall back on their own judgement. So if he thought it was probably onside, the game continues. If he thought it was probably offside, the flag goes up.
On the whole I feel the media furore over some VAR things is over the top. It IS going to take time to work properly. We need to give it that time. If that means some bad calls happen, it isn't really any different from the onfield officials getting things wrong.
I remember the introduction of the passback rule, something infinitely less complex. That was chaos for at least half a season. But because we stuck with it, nowadays it barely gets a mention. I feel if we are patient with it VAR will follow the same, if more lengthy, path