This isn’t an office building, and nobody “hid extra pairs in the wall” for good reason. This wiring is a very specific technique used to quickly feed phone pairs in new SFH and apartment buildings of a certain era when the minor CAPEX advantage of a single shared cable over home runs was sold to developers as a cost cutting measure (or just done anyway to pad wallets when home runs were specified).
You’re definitely right that it uses standard 25-pair color code, but it’s just a six pair residential run here: white from blue to slate, and red-blue.
Apart from the grounding issue, my 16" Pro has done things alone that most of my peers use a laptop AND a desktop to get done. But yeah, if you’re not processing a ton of realtime video, or saturating thunderbolt with network traffic or something, then the Air could do any 2-3 of the 8 things I’m doing at once admirably. And I’d probably be less pulled in all directions. lol.