It's like this... we are ALL under Part 107. EVERYONE who is not flying under a Public Use COA is under Part 107 which means CIVIL Operations. Leave Commercial, Money, Compensation, Beer whatever out of this equation. Those things are under Commercial (which is a section under P107) but 107 is EVERYTHING. It's the BIG circle.
The "Carve Out" only protects the hobbyist so long as they stay within the very precise HOBBY box. Think of it like a bubble. If you pierce the bubble it's gone and you're now sitting in the Part 107 bubble... regardless of your original intentions. You pop the hobby bubble your tail feathers are now in P107 territory.
This concept seems so simple, and yet causes such endless confusion.