No. I was never told that.
I was raised by my father, with no mother present in the household.
When the need arose to give me an enema(NOT often!) The way he handled it was to tell me, "you need to try to take all of it! Neither of us wants to spend the whole day in here with your enemas. If you CAN take the whole bag, and then hold it 15 minutes, to give it plenty of time to work, that will mean fewer rounds to a clear return. We both want you to get to a clear return in the fewest possible rounds. Let's face it, after 2 rounds we both are more than ready to quit. So just relax, don't fight it, and be a strong girl. I know you CAN do it.
I WAS able to get the whole bag in, and hold it. What he never told me until I was home from college over the summer was that HE was older than I was when he bought his first two quart bag. His first time, he didn't get it all in.
I was always told early on "You need to take as much as you possibly can!"
NOT "You have to take the whole bag!"
Every time I balked at taking the whole bag, it was "Listen! YOU don't want to spend all day taking enemas! I sure don't want to pend all day giving you enemas! You want to get this over with as quickly as possible Don't You?" In that situation it was always "YES!" even if a few minutes earlier it would not have been, si it was always "OK Then One more really deep breath, and I'll open it up again."