Mo, I've only spent a little time with the 20th S in a shop, so my opinion might not carry as much weight as someone who's owned one for awhile, but I don't think it could really do that (granted, you're talking about stuff like Animals as Leaders) without a boost.
Let me rephrase, it can pull it off since it's a somewhat tight amp and there's a ton of gain on tap, but it's a "singing focused mids" type of amp with some Marshall bark and kerrang. Sort of a refined Marshall (tastier gain structure, not harsh at all)
It's sort of like a Mark series amp playing djent, but less 'metal'. Yes, it's tight and can do it, but it's not the ideal voicing for that type of modern music. It's more musical and creamy and just the slightest bit dry, but in a good way. Great for soloing and classic metal/rock/blues/country, etc. Doesn't have that BIG, ultra tight, punch you in the chest sound. It's a vocal amp.
Now, In the studio, double or quad tracked with the proper EQ, it would probably kill for modern metal, as would most gainy amps.
Sorta like my MarkIV and the old 101B white chassis I had- I could pull off the modern stuff with the BB+ pre but it wasn't geared toward it.