Can't let this one go !

Separation DOES occur before the TE ----well before in most cases. A sharp TE increases the flutter possibilities markedly.

Read Dick Hanson above! Kamm "as in Kamm backed cars etc." determined that there was an "ideal" length of taper to create the least drag. Since this is generally "way beyond" the reasonable limits, he then determined that the best compromise was to cut it off flush at the desired point and that, would yield the best compromise. This was proved in actual wind tunnel test and these data are available.

Do a search on KAMM or hopefully one of the real aerodynamicists on RCU, like Ben Lanterman etal will comment tonight. TallPaul already has commented but in a less than pointed way. He too may re-visit this exchange before the evening is over.