This kind of agreements do not work like that. Let's assume there was some kind of deal between Sony and Capcom to market and promote the game overseas. Then Capcom should have agreed on some conditions to prevent the marketing deal to be ineffective for Sony. For example, exclusive betas; no videos of Xbox One version; and so on. But these don't come as "You shall not release any beta on Xbox One!", but rather something like "You shall not mention the product outside shared initiatives" or "You shall not advertise any other product in the MH franchise during the timeframe XX".
I know how these types of agreements work, and what you're saying doesn't make sense either, because, again, if what you're saying was the case, XX on the Switch wouldn't exist in the first place.
It was released in Japan two months after World was announced. If Capcom wasn't allowed to advertise or promote any other Monster Hunter products from this point until the release of World then XX wouldn't have even released on Switch in Japan.
The lack of a localisation is entirely on Capcom. I stand by the notion that thinking the localisation is somehow part of some nuanced money hat from Sony is absurd.