The size and shape of the spines around the areole do look like M. lauii, though the spine colour is closer to M. lauii ssp. subducta.
Normally the flowers would be pink, but I know there is a white flowered form of M. laui itself, so I guess a white flowered variant isn't impossible, though I've never seen one before.
I understand that the white flowered form of M. lauii ssp lauii has been seen in habitat, but it is very rare, so what we can sometimes find in cultivation are probably selected forms.
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Chris43, moderator