The team can learn sign language if they prefers or they can use pidgin. Pidgin is a simplified form of the communication to convey it. Pidgin itself is not a language, it is more of jargon in a sense. Pidgin is very common uses outside of Deaf communities.
Baseball use call signs, and that is pidgin. Crane operators have their hand signs, that is pidgin too! Same for military, they use pidgin. Pidgin is easier to learn than sign language as it can be simple handshape or call sign, similarly to emoji in a way. Sign language requires efforts and you will be surprised to find thousand muscles you never thought you used before.
EDIT: If you are talking about Deaf Team and Hearing Team (people with hearing ability for those folk who are not familiar with Deaf communities jargon) attempt to communicate with each other without sign language, then yes it can be a pidgin. If the Deaf Team itself communicating with their teammates, then it is not a pidgin because they switch to their native language to express.
I assumed that it was like a Battle Language https://dune.fandom.com/wiki/Battle_Language
Other teams do develop their own language, with both verbal and hand signal components. However, I'm not sure high school football coaches are necessarily adept at making new languages, sure maybe it is good enough for what they're doing, but is it as robust as ASL or English? Of course not. Then, the players need to take time to learn it, if they ever even fully grasp it. Then, the players will come and go, so once a senior, who probably fully gets it leaves, the coach is left with a bunch of new players they have to teach - for this reason, the language is hard to refine. For all of these reasons, the team using their native language has an edge in communication.
This is probably better at the pro level since a player on each side has a direct line in their helmet from the coaches and the players stick around long enough to master the new language.
Overall, though, I think this line in the article is downplayed: The coach attributes the turnaround to rigorous conditioning and an especially talented cohort of players, some of whom have played together for years at lower levels. It's a great human interest story to talk about turning a perceived disadvantage into an advantage, but it sounds like, deaf or not, this particular group of players shows great teamwork and a great work ethic.
In this context if the other team did happen to have somebody who could interpret the signals quickly enough, it would be pretty easy for the players to just have a few codes which change the meaning of the signals. And of course you can just agree what codes mean what in the huddle or the sideline where the other team can’t see.
At some point, though, you might confuse your own team more, than the other team, so I would keep it simple, especially if we are talking about a sport, that involves banging heads together.
I read the article and I played football against Gallaudet in college, and I fail to see how that is an advantage at all. We came the line of scrimmage and our quarterback announced the play we were running and on the line we would verbally agree on the pass blocking scheme. “I’ve got 64, you take 73 cause it doesn’t look like the linebacker is coming.”
I suspect they’re succeeding because they’re well coached, very fit and physically talented. And while their deafness is no real liability I don’t see it as an advantage.
This need additional contexts. Deaf communities use Signed Languages in baseball. Outside of Deaf communities, they are not sign language. Language by definition requires grammar structure, cultural information, foundation of linguistic, etc.
They are using pidgin is the word you are looking for. Baseball use pidgins, they don't use sign languages. It is an important distinctive because one is actual language and other are not.
It is not because of people fighting against it. It just that English is damn complicated and not easily to be an expert on it. Written and Spoken English does not have the same discourse style. There are times when I thought I structured it correctly and turns out it not. I am natural-born American and English is my first/second language (ASL is my first). Even English native speakers struggles with it than non-native English user.