I've not heard of such a thing when entering Coz but I can tell you there are some strange things going on with Mexican Customs entering Coz that I view as unusual and there are even stranger things going on in other Mexican international airports. However, at the end of the day, we all are entering a foreign country and if we want to pass through that gate and enter that country we have to be willing to accept whatever search and confiscations they may impose prior to allowing us to enter. If not, we can pack up our stuff, not leave the airport and book the next flight back to where we came from.
A few years ago when my wife and I flew in we witnessed a woman who grabbed her bag from the belt, one of those cheap wheels from her luggage had been broken off in transit and she was raising all hell about that. Perhaps her behavior made her stand out and she was flagged for an inspection. She continued to raise all hell screaming that no one was going inspect her bag and that she had rights and this and that. Everyone who passed her ongoing outburst was probably thinking the same thing we were... That bag is gonna get opened and searched or your're not leaving this airport and will be going back to where you came from at your own expense. If not, you'll be going to jail. Obviously this person must have never traveled abroad before or was just ignorant.
Entry into another country as a foreigner is not a right of ours but a privilege that country may or may not grant us. If Mexican Customs confiscates a few bottles of shampoo and conditioner in those little bottles its not a big deal. One can buy all of that they want at any grocery store.