I suspect my personal experience in the burning regard isn’t the norm at all, but at least it’s something that’s possible for people to experience.
While I definitely have a very major improvement in ability to take sun before burning once having a good tan with MT-2, for whatever reason it isn’t as much as I’d expect from the darkness of the tan.
I’m often a very comparable darkness to my wife, and sometimes darker, but she can take at least twice the sun before any redness.
An interesting thing is that melanin is not a single substance, but rather is a family of polymers, in two broad categories. (Within each category, there can be differences in the proportions of sub-units, so a great deal of variation is possible.) So this is how people do not have simply different degrees of darkness of the same basic color tonality, but also differ in color tone even besides the degree of darkness.
One of the types of melanin is pheomelanin, which can impart a reddish hue. Eumelanin, depending on its type, imparts a brown or even a (roughly) black color.
I doubt, or at least haven’t seen evidence, that MT-II changes the balance of the categories or types of melanin produced.
So no matter how much I tan with it, for example, my color will differ from some given other person’s.
Pheomelanin probably provides less UV protection than eumelanin, and as it happens, my tan has a red-brown (sort of American Indian) aspect to it.
Anyway the point of the story is that while it can provide significant improvement in ability to take sun before experiencing sunburn, when not having the genetic gift of naturally being able to take a lot of sun MT-II may not ever take a given person to tolerance level that a genetically-different person might have, even if the MT-II has provided a tan that in general is as dark or darker.