Yes for the majority of people it is because transplant hair is taken from the safe zone and not affected by DHT, however there are a small number of men who eventually loose some of their transplanted hair when they get old due to their safe zone donor hair thinning as part of the ageing process. Fortunately for most this is when they get to a pretty old age.
bullitnut brings up an important aspect of the question being asked. A hair transplant needs to use genetically healthy hair, not affected by the hair loss gene. If not then a hair transplant is likely not to be permanent. It´s reasonable to expect that some of the hair over many years will thin out a little. Especially if the hair transplant is performed years before. But this amount is not going to really affect the look, coverage or hair density in any major way. But if the hair is not genetically strong the hair used could fall. This is more probably with the FUE technique because it uses a wide extraction zone. There is more chance of taking genetically weak hair. Especially when treating lower hair loss patterns and using a wide donor area. As there is no demarcation zone between strong and potentially weak hair it´s a judgement and ethical call when to stop taking the hair from an area.
With FUE sessions getting larger, now seeing 4, 5000 plus grafts in one procedure there are potential detrimental conclusions. Because of the large number in one procedure transection increases and hair follicles get split. Either left in the skin or partly removed, either way, damage and growth can be impaired. If the extraction is spread out it would need a very wide extraction zone and likely go into an unsafe area. This hair is potentially genetically weak and will fall out over time. This will affect the hair transplant result, design, coverage and hair density.
Either way, it can take a while for the results to become obvious. As it takes at least 12 months for the hair to mature and grow anyway. Weaker hair growth could potentially take a few years to become obvious before starting to thin. The donor hair may not look overly bad to the eye until it is inspected for another hair transplant. The showing signs of miniaturisation, and patchy low areas of hair density. It makes the difference between careful planning and just taking as much as possible with little consequence.