Do you know whether the butterfly pea, clitoria mariana, requires cold stratification/winter sowing in order for the seeds to germinate? Or does it just need to be planted in spring after the threat of frost is gone? I've only been able to find information on other variants of butterfly pea.

That should work. When I grew this from seed it was early spring in a container in the greenhouse. I planted it out in the most inhospitable location and it stood still for a season. If it bloomed the first year I missed it, but it has sown itself pretty liberally on a steep bank in heavy clay, so for me the successful method was patience and neglect.