Reboot drops battery by 2% each time
Yes and no
It does take energy to reboot, but it isn't the phone rebooting that takes this energy. The energy is lost through hystersis which the battery algorithm is accounting for.
Krexington_III, who worked for a summer as a fuel gauging engineer for a major cellphone manufacturer in northern Europe and says:

Hysteresis is simply the fact that once we've got the battery
discharging, if we stop discharging it (say, by turning the phone
off), it will keep on discharging by itself for a short while.

(Paragraph 3)
https://www.reddit.com/r/explainlikeimfive/comments/1qrdc9/eli5how_do_digital_devices_know_how_much_energy/
Phones need time to tell how much energy the battery has, and don't keep track of the battery while it is off. Your phone was programed to estimate that 2% was taken away while the phone was off due to Hystersis. Your other phone does not make this estimation (the user won't notice).
I suggest reading Krexington_III's post for (a lot) more information on how phone batteries and their algorithms work.