Its more to cover things like insurance and the data protection act. Had you not had the signs up, the other party could have had it thrown out as inadmissible, as it is against the law for a commercial property not to have signs if recording cctv
footage. This would obviously depend on how good the other parties legal representation was, and how serious the case was.
I had to do a few video retrievals for court and always put them signed, dated and verified as an "identical copies" in security sealed evidence bags. It wasnt asked to be done that way, but provided just in case the validity of the footage was brought into question.
Just because it wasnt asked for, doesnt mean it couldnt have been asked for.