The key word here is “appreciably”. While it may slightly improve stall characteristics and maybe add some fraction of a knot to cruise speed, I doubt it “appreciably” affects anything since the gap/and wing is very similar, in some cases identical. The only
difference I can tell is the tolerance for the gap is slightly tighter for the early 20, probably due to not having a gap seal. So you might end up with less overhang of the seal, causing less change/improvement.
My point was it shouldn’t take 250k to put a darn gap seal on.