Sub appearances are probably not inherently intense, true, but here we have evidence that Lookman's appearances have had that intensity. He has been coming on early (often before the 60 min mark) and then making a difference in important games.
Might be talking out of my arse here but yous are maybe taking about different sorts of intensity.
The type of intensity in which you need to change the game, usually through individual ability, is one thing and usually associated with the sub appearances. I’d say having to change the game through stepingn up and making something happen is an experience he’s had on loan deffo and to me it looks like he’s done it well.
But the type of intensity which is more sort of an intense and close following of a tactical plan e.g shapes and triggers, when to close people down when to look for the break, which man to mark and when to mark him closer than other times (probably a bunch of other coachy type stuff as well), that type of intensity is different but imo more like what you’d be sent on at minute one with.
Or if you are a CM/CB/defensive forward player the sort of remit is have to follow if you get thrown in late (to first keep a game rather than to try to change a game).