TLS 1.3 is IMHO still too new to have stabilised and had all the edge-cases worked out. 1.2 was first released in 2008 and only started becoming a requirement more than ~10 years later. I'm not sure how the situation with 1.2 was but I know there were several draft versions of 1.3, which do not interoperate yet had public implementations. That might be what's happening there.