Hmmm...I think that makes sense and is probably a good example but it may point to more fundamental problems which these things often do.
As great as deads are you shouldn't HAVE to do heavy deads in order to squat well of course. That is not to say you won't need lots of posterior chain work. But I take it that you had missed a more than just one or two dead workouts.
Theoretically once you've "taught" your abs to fire properly during squats and you continue regular squatting they should continue to do the job. The term "theoretically hardly ever means anything in the real world though
However, in this case you might want to look at movement patterns and postural problems that the squat could be reinforcing leading to imbalances. Maybe when you do deads it balances things out more and so what you are seeing here happens. I don't know of course but in the end what you want to achieve is overall more balance and not a continual tug of war between one "balance" and another.
The routines many of us follow are not nearly as "balanced" as we have been led to believe. This is where many of the injuries we get come from rather than just over-use or acute injuries related to a too high load or whatever. The 5x5's we are so very in love with are not balanced at all from this standpoint, if fact.