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 ?
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.
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.