There are always going to be variables in everyone's lifestyle and diet. Hard to pinpoint sometimes what makes the difference. It is fairly explicit when it states that 'a healthy dietary pattern was positively associated with total gluten avoidance'. This shows that taking into account variables following a gluten free diet was healthy.This paper is looking at different variables. It doesn't assess the effect of not eating gluten on the body, which is what the papers I saw were assessing, so not really comparable. The link between the gluten free diet and the 'heathy dietary pattern' also seems dubious to me. Here they defined this as 'higher consumption of fruit, vegetables and lower consumption of dairy products, salty/sweet and fatty foods and alcohol.' I haven't got time to read this paper in full at the moment but I imagine it would be very difficult to guard against confounding factors here e.g. how many of those people already ate this way?
Worth pointing out that they also found these people were more likely to be female (haven't looked for this, but a sensible guess is that women are probably more likely to buy into fad diets because of ED culture) and people with a lower educational level (who might not know how to assess the evidence).
Here's one paper which is open access:
Cutting out gluten where not clinically indicated can result in a decrease in fiber consumption, potential decreases in mineral and vitamin consumption, including calcium, magnesium, zinc, vitamin B12, folate, and vitamin D, and potentially increased exposure to dietary hydrogenated and saturated fatty acids, and arsenic
Yes, I take your point about gender and lifestyle. I think around 80% of vegetarians and vegans are female, for example. I imagine many people who follow a gluten free diet already lead a fairly healthy lifestyle and many would probably be female.
I also accept that there are concerns about following a gluten free diet. You need to make sure you take in grains from other sources. Do your own research and talk to nutritionists! I understand you seem unsure about nutritionists and that is your choice. Look for qualifications and find reviews on them like you would if seeing a physio, for example.