this case is overstated


it's only going to be the 'base case'/'cooperative case' that will become indistinguishable, e.g. Lightning channel opening transactions and cooperatively closed channels, because Schnorr "additivity" (which is not a real word ) makes such transactions appear the same as a regular 1 (or more) inputs -> 2 outputs tx, because there is only 1 signature (because additive signatures). Currently, spending outputs from that kind of transactions reveals it to be a 2 of 2 multisig that had alternate script paths, not so with the same script using Taproot/schnorr.

Uncooperative closes are still distinguishable from the regular 1+ in 2 out transactions, because of the atypical script they use will (necessarily) be revealed if they are broadcast/confirmed in a block. I know, uncooperative channel closures are not common, but they will still sometimes happen when using Taproot/schnorr based channels/contracts.