Is lengthening easier when you are taller?

The recommended amount for tibias is 5cm, but would a person who is 180cm have a far easier time lengthening by 5cm than a person who is 160cm?

No, it's bias. Every person will have difficulties lengthening past safe limits defined by top surgeons in the world no matter the starting bone length. It's about 3.5 cm for tibia and 4.5 cm for femur. It gets progressively difficult going above those numbers. But, the longer the starting bone length, the more natural looking one will end in terms of proportions and biomechanics if he lengthens the same absolute amount compared to someone who has relatively short starting bone lengths.

For example, someone who is 160 cm and has 30 cm tibia and 38 cm femur will look bad after 5 cm tibia and 6.5 cm femur in terms of proportions and also will hardly adapt to new biomechanics rather than someone who is 175 cm and has 38 cm tibia and 48 cm femur. That's because 5 cm lengthening is about 16.67% of original tibia length for 160 cm guy and 13.1% for 175 cm guy. The same goes for femur.

The closer the lengthening is to 10% of original bone length, the more natural one will look and feel in terms of biomechanics.

A person who is taller will have a much, much easier time lengthening.  5cm on say, a 6-foot person will require much less tension and stretching on the soft tissues than someone of 5 feet.  To oversimplify, take a rubber band that is 6 inches and one that is 12...same exact density, and now stretch each one out an extra 5cm.  There's far more tension on that shorter one.  A lot of people on here think that 5cm is 5cm, and it will affect everyone the same, regardless of starting height.  So yes, the larger you are the less painful lengthening will be.  I did do it, and the taller people there had an easier time.

i dont think theres enough experience to know this as 6 ft ppl are not crazy to do leg lengthening. and if they do would they share their experience and have multiple ppl saying the same thing for u to find out?

I'm 1m87 and I've already asked this question to Turkish surgeons. Out of 3, 1 thought it was easier for short person, 1 told me it was easier for tall person, and 1 didn't notice a difference