Nothing fractional, and nothing custodial about a Turbo channel.
fractional:
"There is no concept of what LN "allows". Channel rules are established between the two parties that enter them, it is voluntary. That means you can agree to any rules you want."
which is my point. 2 parties can agree to a LN balance even without proof of btc collateral
custodial:
"The risk is Bitrefill's because we are fronting the BTC in that channel "
turbo:
no confirm = no locked collateral when the channels is "fronted"
yea you can try to explain how your non turbo fee's havnt changed, but thats just a meander off topic. thats not admitting the truth, thats explaining a left hand when everyone is interested in the right hand (totally irrelevant)
the safe way a system like turbo works would be that turbo is factory based. where turbo just hands out HTLC's of balance in msats that CANNOT b broadcast to bitcoin. but instead the other party has to hand to the factory for the factory to settle