To attempt to answer my own question:
There’s some depth here; at least two questions: is Shor, or a variant of it, in the QC scenario, proportionately easier for smaller discrete logs in 1 group? And: is solving a “small discrete log”, size p, problem on a larger curve the same as solving a general discrete log problem on a smaller curve/group of order p?
For the first question apparently this paper shows an algo that allows you to use Shor/quantum to solve discrete log proportionately more quickly for a shorter discrete log. Apparently there are follow up papers that address cases where the discrete log is shorter but not half as short (i.e. I think that paper only covers where d, the discrete log is less than sqrt(curve order), i.e. half bit length or less; I think later papers more or less generalize the result to larger bit lengths).
For the second question I don’t know, seems a little less clear? If the Ekera algo in the above paper tweaks vanilla Shor, so it’s actually a different algo if admittedly still similar (period finding, aG + bP etc.; I don’t know the details). So is it “the same” to solve a 192 bit secret on secp, as to solve a same-size secret on secp192r1? My guess would be it should be very similar, but strictly not the same.
Given that lack of clarity on the last part, I’m not sure if there’s really much of an argument for using DLEQAG vs just a range proof of the size of the secret; I don’t see what it gains you?