I agree, that is not a good idea. Also, mango is monoecious and self-fertile, meaning you only need one tree to produce fruit.

CORRECTION: "to make a thin incision" (instead of "to cut"), all the way from the roots up to the top. That does not remove the bark, only makes an incision. Is it still bad advice?

Never heard of that. Mangoes like dry spring weather and lots of pollinators active,mainly flys.

I was once told to pile up soil up the trunk of a citrus tree (orange) like a pyramid cone to retain moisture and that also was by a local Azorean. Perhaps Azoreans have special ways to treat their trees. Newcomers and foreigners are advised of ways to speed up fruit bearing and every useful advise or debunk is deeply appreciated.

It sounds as if the mounding of soil at the base is version of mulching but moisture on the trunk is not healthy for a tree as it poses other problems of pest, fungal infection...