No. That's why it says "as if you spent team".
There's plenty of verbiage available to a PbtA game to indicate other kinds of boosts - you can see other playbooks using +1 forward and +1 ongoing to describe many kinds of bonuses. If the Nova was intended to provide a bonus to another hero's roll, completely separate from the team pool, it wouldn't even need to have mentioned the team pool in the first place.
"As if you spent Team" means the limitations of the Team pool apply. The Nova can spend a Burn with the Boost flare, or spend from the pool, but either way that's their contribution, and you'll need allied NPCs or other heroes to boost the roll further.
So the Nova can't:
- spend all the Team out of the pool by themselves, but you already knew that
- dump all their Burn boosting an ally's roll
- spend a Team and then a Burn
- spend a Burn and then a Team
because spending Burn on this flare is like spending Team. Except it doesn't require any teamwork or a tough choice on a roll to Protect Someone, it's just the Burn the Nova gets all the time to do anything.
If you really need a second point, there is literally nobody else around to help, and there's Team in the pool, the hero you just spent Burn on will probably be able to spend Team to act selfishly and shift their own Labels. There's all kinds of potential to act selfishly after someone just helped you.
If you really need a third point, maybe just take the L.