I think it mostly depends on the location where microphones are within the stadium itself, otherwise I would not be surprised if it was revealed the teams and the head of the clubs decided it was important for their business to keep the façade of an intense match in the eyes of those who would be watching from homes.
I have seen live matches and I have been in a couple of matches myself in the stadium and it could be realistic for people to get more fired up during pivotal points of the match.

I stay undecided on what to believe in this instance.
I would be sad to realize one could not even trust the passion of the people during a match to be real and those with the rights of transmission of leagues need to resort to this manouvers.