That population is shrinking. Having worked in very large (investment) Banks, other parts of the finance sector, the move is generally to divest from thick clients to web. The whole COVID situation pushed this along even faster with the reliance on diverse VDI solutions, which don't necessarily play very well with crummy in house thick client apps.
High performance, low error-tolerance applications previously only available to Windows are a continuing lock-in, yes - that's part of why gpu drivers are such a big deal.
There have been working comparability layers for the various hard-to-run on anything but Windows software appliances, but a major sticking point has been the GPU support (which keeps the software running well).
I don't think this will be true forever though, graphics drivers continue to make strides in being more open, often to the benefit of the various organizations writing or purchasing the gpus/firmware/drivers.
