All right just to clear up terminology, the standard ace sequencing techniques don't require any deck estimation, just memorization of key cards. Most casino shuffles use half-deck grabs so quarter deck estimation won't do you much good in standard shuffle tracking either. The power of the zone type of shuffle tracking is increased with the resolution of your deck estimation and division, but variance goes up with inaccuracy of dealer grabs when you get too fanatical with resolution. In some 8D shuffles dividing the shoe up into four 2D segments gives you plenty of advantage.
Then there is the subjective, visual type of shuffle tracking that requires merely following a pack of cards through the shuffle. No deck estimation of any kind is required for that, just excellent visual skills. My visual skills and deck estimation aren't that good, so I concentrate on sequencing and binary cutoff tracking. But full deck estimation is more than enough for counting. Every simulation ever done proves this, and also that rounded indices are almost as good as exact.
While it's true that a counting error per deck could add up to 5 by the end of the shoe, the odds are only 1 out of 16 of that happening. The odds of the high cards being on the other side of the cut card, leaving you betting into a non-advantage situation are much higher. Counting errors like that leave you nowhere near negative EV.
Nonetheless, the fact that the variance we are playing against dwarfs the effects of random errors is no reason to not reduce errors. I'd be the last one to tell a player to play carelessly or using a technique he is not ready for. But let's keep it real. It is very important to me to know the magnitude of both the advantages and disadvantages we encounter. I don't buy it when people overstate the advantage we can play with nor when they overstate the risks.
Not to tell anyone else how to play, but this is the Prime Directive of card counting- "Wait until there are a lot of aces and 10's left, then bet a lot." Everything else is just a detail, particularly the exact definition of the word "lot." But if you follow the Prime Directive, you are playing with an advantage. Even players of weak systems like Ace-Five are playing with an advantage.
