I'm wondering the same thing... they also used snips to cut the trim... judging by the language of the title, it may be some cultural difference. We certainly do not do it like this in Canada. The shimming and leveling of the jamb, sure , but not screws and cheap casing. Plus, they dont even show feigning the shims off before fitting he casing. I'd say this is about a 6/10 video Edit: it's a fire door, and they're using a hammer drill. So that drywall is probably covering cinder blocks. Hence why they'd have to use a hammer drill to hammer the "screws" into the cement. I watched it twice and realized I wasn't seeing some things the first time.

These are hammer in screws. They come with specialy designed plugs. You just hammer them in and can unscrew if needed.

Is mastic only required where a long duration fire rating is required?

Depends on the test evidence for the door, would expect minimum of mineral wool and mastic though but the architrave / trim could be a tested method suitable within the assessment