I think that's a working theory! But hard to say if it's reality. For example, 2 weeks ago, 3/4 (actual Mardi Gras Tuesday) had LLMP for a high amount - want to say $39 for MK, which indicated to me, big crowds. Then for those of us who still need park reservations (APs for us), they made that day a 'Good To Go' day, which meant no one needed park reservations all day, which I thought indicated a low crowd day! So it's a definite maybe on your question!
BTW - 3/4 was a pretty busy day at AK that day - not sure about the other parks, since we only did AK......