Not Knowing a Rule

You ever just realize you have been playing/coaching for a long time and you just never knew/totally understood a rule that you thought you did.   To start the 2019 season, we had our scrimmage to start the season.  We had an official who I believe is fairly "high up" who I have had a couple times in these scenarios, who likes to bring both teams together before the game starts to give a speech and tell the boys of the different rule changes from the year before to this year that they may need to know.  Either way, last year, one of the rules he said, (I will say I never went back to him to make sure that I heard him correctly because I was just dumbfounded), was that this year there was no more tripping on defense.  I think he even said like "you know, it used to be you just do whatever you gotta do to get a guy down, but there is no tripping now."  Could have heard him wrong, but don't think I did.  Either way, I must say the biggest reason I didn't go to him and ask was because I was just thinking to myself about how many tackles I missed where I could have been tripping someone.  I mean I set a record at my school for career tackles, and I'm thinking I should have set a world record because if I had known I could trip, I would have been hell on wheels for any ball carrier.  Like I say, it is totally possible I heard something wrong, but I swear that is what I and other coaches on my staff took from what he said.  I'm still mad about that.  Haha.