You’re mistaken about the pain, what I witnessed indicated little sensation at all when the needles were inserted. And, he wasn’t restrained. He laid there calmly. Had he seen the needles it would no doubt have been different, but the holistic vet was good, she kept him entertained and distracted while she inserted them. He was happy as a clam the whole time.
The part I bolded is key. Distraction can truly take one's mind off pain, and with a mild pain such as having needles inserted, the distraction may be enough for your pet to not even notice the pain caused by the needles.
If you are aware of the Lamaze method of childbirth, the principle is the same. The pain of childbirth is severe, but concentrating on the breathing patterns helps to focus the mind on something other than the pain, making the pain more tolerable.
A giant lizard, however, is not a pet and cannot be distracted in the same way. All I can think of is that the poor animal is being subjected to a lot of stress and pain for no real medical benefit whatsoever. That is cruel.