Next time, I'll know how to post the photo link in the actual post.

Here is a link that might be useful: Pictures

Not sure they do - maybe not enough color in the leaves and too much color in the flowers - but if they fit the so-called purple Labrador violet then they are correctly Viola riviniana 'Purpurea'. It was never accurate to call this V. labradorica as that is actually a different species perhaps not in cultivation. Yours may seen seed around more on their own, without assistance. Otherwise you could buy some more to increase the planting, it's certainly not a scarce or expensive item.

They should spread on their own, don't worry. You could divide them if you have a thick clump of them. It does kinda resemble Labrador violet but not quite. They may be less purple from shade, but still don't quite resemble Labrador.

They may have some trouble seeding in the bark mulch. Bark mulches can be hard on annuals and perennials spreading, that's part of why people use them, thinking of weeds. You might have to help them by planting.

I've been checking the plant centers, but not finding these so far.

I did kind of want to try transplanting some 4" clumps. (It is a dense patch.) But not until they're done flowering, I think. How does that sound? Any tips for increasing the chances of successful transplant?

Cool/cloudy day and keep as much soil as possible around the transplants when digging. Dip exposed roots in water every few minutes if the procedure is taking longer than that. Focus on matching the planting depth to the surrounding soil level. Make slightly tapered planting holes instead of vertical-sided--this helps to merge the infill soil and prevent a "crack line" around the transplant later on. Use firm pressure when doing a final pressing-down of the transplant. If the soil is still damp, no need to use a ton of water, but keep a close eye for drying soil during warm spells.

"How to discourage violets from spreading" would be a more common topic. Had to remove ours--spread too readily.

Yes larry gene I agree.
I've had a persistent patch for years that I've been pulling up whenever I see them. They're in among some Cyclamen hedera and Heath. I'm always wary of plants that are difficult to eradicate and surely don't want more.
Mike