I know I will sound like a broken record bu tif anyone has any questions and would like REALLY thorough answers from someone who knows his stuff---ask Bob Mac. The man amazes me each time I read his articles/findings and even his personal email.
With your permission RG I will post this to his group and ask for imput and then post it here---but like Ed pointed out---tubes are tubes. MVB's are a different animal. And not even all of those are create equal.
I have one bulb that I paid a fortune for that was putting out numbers like 8---understand that some quality bulbs put out numbers in the hundreds when first turned on. 8 is like---worthless for even heat. Yet this company has the nerve to charge 46 dollars for ONE bulb.
I am more and more impressed with Trex products. But to be honest zoomed is coming out with some superbulb that is supposed to blow the others out of the water...so lets see

But to answer your question---while some species are debatable for d3 supplementation Vrs UVB radiation---iguanas are not one of them. They need UVB to be healthy in any way.
The place an animal comes from has a serious bearing on what type of and how much uvb they get. This has been proven though blood tests after exposure.
I have Bob's permission to repost his findings and certain answers so I will if you wish, copy and paste this post for him to review.
You could if you wish even email his yourself---or I will do it---it really depends on what your comfortable with. Let me know
