Commonly, before a broadcast football game you will see the positions of each team's players on the field. Now since this can't be enforced as a rule, wouldn't it be strategically benificial that coaches lie about who's playing where ? Although the names of the players composing the squad are verifiable, their actual positions aren't. Does this ever happen ?
Actually the coaches usually don't talk to the press about their formation at all. So there's no need to lie.
At least in the DFL and DFB rules there is a clear procedure, because it's done online (for almost any official competition in Germany, including the Bundesliga):
- Team A reports their team (starting 11 + subs, goalkeeper, captain)
- Team B reports theirs
- When both teams have confirmed their team it will be locked automatically and made available to the officials and the opposing team
- In the pro leagues the home team now has to take care that the press gets a (printed) copy (usually done by a media representative). They usually look like this:
So since there is no official report about the exact formation we can safely assume that the formation on the screen is a good guess based on past games and the position players usually play. Sometimes the coach talks about the formation (something like "We'll play 4-3-3." without mentioning names) in the press conference before a game, but usually they don't.
It'a actually as simple as the broadcasters making an educated guess based on previous matches. If a team is playing the same four defenders as the previous match, the broadcaster assumes the team is still playing a back four with players in the same positions. Uefa do this as well with their teamsheets.
There are often occasions where play starts and the commentators point out x team are actually playing a back five, for example, if this formation was unexpected beforehand.