No, I think you have that backwards, it's the other way around.
"Mango trees from nuclear seedlings are identical to mother plant. In polyembronic seed, the zygotic seedling will either degenerate or be weak, stunted. Nuclear seedlings can be distinguished from zygotic on the basis of greater vigor one month after germination" R E Litz. The Mango: Botany and Production.

Seems to be confirmed on GW tropicals forum -

Here is a link that might be useful: polyembrionic mango seedlings discussed here

Cheers thanks for the help