OK, here goes.
Tibouchina lepidota became Andesanthus lepidotus and has a different stamen disposition compared to the Tibouchina that became Pleroma.
The 'white one from Fox Rosehill' has stamens arranged like the Tibouchina that became Pleroma. And note that the stamen filaments are clearly pink.
Separately, and without collusion, two of us thought it might be the complex Australian hybrid being sold as Tibouchina
'Peace Baby'. In 'modern' taxonomy that would be Pleroma 'Peace Baby'.
As supporting evidence, 'Peace Baby' is sold by Cross Common Nursery, which I think Matt said was the source of his plant. It is covered by Plant Breeder Rights, so can't be propagated for sale without paying royalties.
Everything fits apart from the reported size of the mature plant.
Chad