Incoming autism. Here are some observations:
In some trailers, Pokemon stats have been fixed 0 IVs and 0 EVs. Usually this is done when an unevolved Pokemon is used to showcase a certain move or ability. Example:
https://www.youtube.com/watch?v=9Ojd6FzTaEM&t=47s (0:47), Eevee needs to have 0 or 1 IVs in order to have a HP of 115 at level 50.
In other trailers, they have been set to 31 IVs and 252 EVs, usually when a legendary is showcased. Example:
https://www.youtube.com/watch?v=HuaL_hMpPaM&t=44s (0:44), Kyogre can only achieve 404 HP with 31+252. Interesting to note is that Groudon's HP is neither maximized nor minimized.
Then there are also trailers where the stats are completely random and not fixed, which is usually during "natural" gameplay like when facing off against NPCs or in online battles. There are several instances in this video (
https://www.youtube.com/watch?v=BeKMDVos_Sk) where Pokemon have stats that are neither minimized or maximized, like when Staraptor is in a Sky Battle or the Pikachu in Battle Spot near the end. Froakie and Noivern have minimized stats though, but they fall into the first group.
The Battle Royal stats would likely fall into the third (random) group. However, unless it's a little cup and everyone has been lowered to level 5, I think it's safe to assume that EVs don't apply. This means Rowlett's base HP is somewhere between 65 and 89.
TL;DR:
If the trailer is showcasing a weak Pokemon or ability, stats are minimized.
If the trailer is showcasing a legendary or "important" Pokemon, stats are maximized.
If it's showcasing natural gameplay (i.e. wild pokemon battles or multiplayer), stats are random.
Rowlett is Tepig-tier bulky.
