I know this might be a bit of a reach; but on the subject of the Gyms this leaker talks about:
-The Galar map has 3 Gyms kind of close together - the Grass gym, a (presumably) Water gym, and something that looks to either be Ground or Rock. It's not unfeasible that those are the first three.
-Considering the leaker mentions Nessa's gym has a water maze challenge, it's probably accurate to say that she's the Water Gym Leader.
-Kabu is slightly more unpredictable because there's no real indicator of what type they use from their challenge, but for the purposes of this I'm gonna say they're probably the Ground-or-Rock Gym Leader.
-The leaker mentions the fourth Gym is Fairy type. On the map, slightly above the Ground-or-Rock looking Gym, there's a small town with a Gym that has purple colours on it; normally I'd associate that colour with Poison or Psychic, but Fairy could fit as well. The town it's in has got large, brightly coloured mushrooms - normally those might indicate Grass, but since we know that's taken, Fairy is my next best bet for it. Which would fit with what the leaker said.
also on a slightly random note, from what I can see on the map there are only 6 gyms; the 4 I've talked about, one in the mountain regions (above and slightly to the right of what looks to be the Water one - but even though they're close together, Ice type gyms have typically always been reserved for later in the game, although it is also entirely possible we have a more earlier one this time), and one in the large city (it's coloured red, but it does look slightly different that the others so it might be something else). Could it be possible that there are less Gyms in this region than we're used to? (although it's also possible I've just not noticed them, or they're a bit more hidden from sight for whatever reason)
It's probably a very big stretch, but it could potentially indicate that maybe this leaker has some correct info.