I'm extremely skeptical that a big chunk of people in such a highly online country just left their phones at home. Maybe some of the Hardeim but I would guess 95+% of people wouldn't do this.
Would you really bring your phone with you, when going out for a beer or coffee, even if it could easily result in you being forced to stay quarantined for 2 weeks?
Is your smartphone really that important to you?
Even though I have personally stayed socially distanced and worn a mask everywhere it was required, it makes perfect sense to me, after seeing how a lot of people have reacted to the pandemic, that a good portion of the population, would let their phone stay at home, so they would not risk a police enforced quarantine.
In israel, this was done centrally by cell tower triangulation rather than app/os, so no way to opt out even with dumb phones. However, reliability was not very good - e.g. people got notice that they must quarantine because a neighbour 2 floors up was positive, or because they stood outside a wall of a closed room where a positive person was on the other side of said wall. The appeal process was initially non-existent, then slow and cumbersome - so the risk of being "jailed" for 14 days due to false positive was small but serious.
What happened next was people stopped going out with their phones, because any exposure would result in a Police enforced 14 day quarantine