If you buy a Tibouchina at a garden center today, there's a decent chance its correct scientific name is actually Pleroma. This isn't a mistake on the nursery's part so much as the plant world being slow to catch up with a genuine taxonomic revision.
What actually happened
In 2019, a molecular phylogenetic study led by researchers examining the Melastomataceae's Tibouchina clade found that the genus, as it had traditionally been defined, wasn't a single coherent evolutionary group. Based on that DNA evidence, a large number of species previously classified under Tibouchina — including the widely cultivated Tibouchina urvilleana, the plant most people mean when they say "Tibouchina" — were reclassified into the resurrected genus Pleroma, while a smaller number of species stayed in a much more narrowly defined Tibouchina.
This kind of revision isn't unusual in botany. DNA sequencing has reshuffled the boundaries of plant genera across many families over the past two decades, as relationships that looked clear based on physical appearance turned out to be more complicated once the genetics were examined directly.
Why the old name is still everywhere
Horticultural naming moves slowly, for practical reasons. Nurseries, plant tags, gardening books, and most retail supply chains still use Tibouchina almost universally, because that's the name customers search for and recognize. Botanical databases and recent taxonomic literature increasingly use Pleroma for the reclassified species, which means you'll see both names depending on whether you're reading a plant tag or a scientific paper.
For a gardener, this mostly doesn't matter day to day — the plant's care needs haven't changed, only its filing cabinet. But it's a useful thing to know if you're ever cross-referencing sources and the names don't seem to line up.