I think it is a bit difficult to define "Low Aspect" ?
When kitehydrofoiling started for real worldwide about 5 years ago, many learned on low aspect wings, like the Carafino or similar, REALLY low aspect.
When they changed from these, to a small high AR Spotz race wing t.ex, they all said it was like "learning all over from the start" again, almost
But things have changed a lot...
Today many low AR wings are quite fast (and not as low AR as back then, so I think most are actually medium AR today), and race hydrofoils are way more stable, as stability is improved in order to be able to handle more power better, and also because design in general are more developed now.
So IMO there is not that much difference today, going from low AR to high AR race wings - not that big a deal and to your question: "How long did it take you", I will say anyone who can ride a low AR can jump on a smaller high AR and ride straight away no problems
Of course carving and jibing and so on will take time to learn - but to just "ride", easy.
Having said that, those trying to learn on these when never having hydrofoiled, some learns on these without much fuzz, but a few borrows an "easier" wing while learning (having tried the race ones for some days), and then jump to their race gear later after having learned on something easier.