Switch sales don't seem that different overall in Japan tbh. 30k (Switch) vs 80k (PS4) but the first figure is half a year vs the second being one year and a half. Honestly just seems like they dont have the resources to make a simultaneous port release, either that or they assessed the situation and found going with the PS4 only to be more cost effective and more important (which it is).
Looking at the platforms Falcom produces for would tell you what you need to know.
They prioritise PS , and even PC over all other platforms.
They have rarely ever supported a Nintendo device