Well, if I were looking at selling an $8600 bike, I would say whatever the prospective buyer wanted to hear, too.

I spent a lot of time car-free riding utility and commuting in an urban environment (unexpected bad pavement, bad drivers, curbs of various heights ... ) in all kinds of weather. I tried every kind of bike including a full-suspension MTB. In my experience a fork doesn't do that much for pavement riding, unless you deliberately seek out potholes and broken pavement, in which case you are abusing your wheels and might end breaking spokes.

Another issue (for me) is that a commuter bike tends to get scuffed up and scraped as it tends to get locked up wherever. Maybe you have a designated and protected place to lock your bike, but even just road grit, stones, the occasional contretemps with cars ... plus the bike might be left in less than secure lock-ups (in front of stores, behind factories, whatever) which means theft and sabotage is a potential issue. That might not be the case for you.

Also possibly not your situation, but I always carried panniers and/or a trunk bag, and most MTBs are not set up for racks. If you are looking at a hard tail, racks can probably be adapted .....

If I was going to drop $8000+ on a bike, I would consider very carefully what I needed that bike to do and I would make sure the bike could do it really well. A cross-country MTB is not designed for commuting ... for that kind of money, you could buy a frame, an AXS group set, great wheels, and a frame and have the shop build a bespoke bike perfect for commuting.