I'm trying to nominate the same ships for Fire Emblem Three Houses and Fire Emblem Warriors Three Hopes and I'm getting an error. Should I be treating the two games as a shared universe?

FEW3H is set in the same world the original game FE3H but it's basically an AU storyline. Most of the cast is the same with a few additions. The two games are listed separately on Ao3 and have been treated separately in other exchanges I've nominated them for. Can you please advise? I can provide more details if it would help.