First, 50% of the time (roughly) BkB players actually play D. Recently, NU has been primarily playing m2m D, so the NU D scheme is simply to ask each player to guard a specific opponent. I am pretty sure (correct me if I am wrong) that under most game situations Lindsey (and similar) guards (no pun intended) an opposing player that in the traditional terminology that most major sites use is called a guard, whereas Law guards one that most view as a small forward. Would you bet against that? I'm pretty sure I'd win that bet.
Secondly, actual stats (including offense) are consistent with the claim that Law actually plays closer to a traditional sF, while Lindsey's actual role is close to that of a (traditional) SG. Both averaged slightly over 30m, and are physically comparable (Scottie a bit shorter but also a bit heavier which makes him more compact, which helps, for example, establishing position for rebounds). If they were playing very similar roles, key stats would be very similar. Are they? Not really.
Reb: Law pulled down almost 6 pg, whereas Lindsey was under 4, with Law pulling down almost three-times as many (300% more) OR. You may claim that Law just happens to be a MUCH better rebounder, for whatever reasons. A more plausible explanation is that Law simply tends to play closer to the basket, which gives him a far better chance of pulling down Rebs.
3P: Law had a higher success rate, but Lindsey actually took far more (5.6 vs 4.1), which is also consistent with Lindsey playing farther from the basket (as a SG would compared to a sF).
BLK: Law had significantly more blocks (0.5 vs 0.3), again, consistent with the sF vs SG roles.
A: OTOH, Lindsey had significantly more assists (2.3 vs 1.8).
And so on.
The actual stats support strongly the claim that, however their roles are called, Law actually did play the role of a sF (or very close to that), whereas Lindsey's role was (very close to) that of a SG. The traditional terminology seems to work well in this case.