For me, the biggest flaw with seedless architecture is how much control the user actually retains over recovery. If it’s not possible for me to independently recover my Bitcoin without actually relying on the company or their services, then how exactly is that self custody?? Convenience no matter the level should never come at the expense of complete control over recovery, because losing access to a wallet is just same thing as losing the funds permanently. If anyone wants to consider this approach then the first thing they should consider should be how recovery works as well as what would happen if the company actually shuts down, but my best advice would be to not even consider such an option.
A very good percentage of Seedless Frame works gives users limited control, such not enough for them to have access at almost every or anytime they want, to a large extent, that gets to be controlled by the system, only that they get some level of security and responsibilities tied around the system for the safety of their asset, although limited, but can be when rules abided with. Personally i don't consider such as self custody, because the idea of self custody is supposed to give you the utmost control at all levels and not some conditioned and restricted form of control still in the guise of self custody.
Considering such should be mainly for the purpose of exchange or trades, and probably peer to peer transactions, other wise, for the purpose of investment, i consider it too risky, because like you have said if the company folds up, what happens to the funds?.