It just means that he hates the appearance of stripped walls more than he hated the original wallpaper.
And possibly doesn't have much faith in the idea that you'll have it sorted, finished and tidied away as though nothing has happened by next Christmas week.
I can just about manage 48 hours of disruption if everything is cleaned up though the process and it's simple to move about without risking knocking things over, not being able to find stuff or having to clean emulsion off the cat five times. I absolutely detest it when everything is all over the place, there are bits and pieces, scraps of paper, paint cans, dirty paint brushes and general shit everywhere.
One of my exes was happy to be described as 'a messy worker'. He didn't believe in clearing the area so it was easy to work in first. He didn't believe in tidying up as he went. He didn't believe in putting things back to usable in the evening. He was a lazy, messy git who wanted everybody to be disrupted so that they appreciated him more at the end and were so relieved at the end, they wouldn't mention that he'd trashed a brand new carpet, clothes, failed to match repeats or anything else he had fucked up in the process.
When it came to me decorating by myself, I only did things that could be completed and tidied away easily in a day. I found that doing it like that made it so much easier, fewer mistakes were made, there wasn't the same level of damage, chaos or waste. I decorated my bedroom in 24 hours, just moving out the furniture I need to, masking off the relevant edges, covering things that couldn't be moved, and then putting things back as they should be before moving on to the next wall. It was easy, relaxing and enjoyable. So I did the bathroom, spare room, living room and kitchen whilst being able to function normally.
Are you a messy worker, or do you clean everything up as you go?
Your answer will clarify whether he's being grumpy or whether you've now made the place look like a bombsite for the next six weeks.