The gate threshold voltage Vgs(th), for an IRFZ44N can be anywhere between 2V and 4V. What that means is that if you buy 2 MOSFETs, one could have a Vgs(th) of 2V an the other 4V.
3.3V will never turn on the one with the 4V Vgs(th) but will partially turn on the one with the 2V threshold.
You just happen to be very lucky and bought one that has a Vgs(th) less than 3V. You might not be so lucky with the next one you buy or even the next 1000 you buy
The term “logic level” is a meaningless marketing buzzword.