Well, if you have applications for 13mm cores, why not just do the same thing but 21.24 times higher power, for the 36mm cores?
Perhaps what's missing is an understanding of scaling laws. Anything you can do at 1W, works at 100W, or 1,000,000W. Well, there are good reasons not to do exactly the same thing across those scales, but the basics, the power flow architecture, is more or less there, and the majority of differences lie in the control schemes (as that 1MW unit will be much more expensive, and it's wise to add some more subtle control and protection features, safety interlocks, etc. to protect that investment, and those working around it).
The actual ratio will be a bit lower, because temperature limits tend to go as 3/2 power, but there are ways to scale faster as well, like running in deeper CCM to reduce core losses. Or maybe the 13mm model didn't get particularly hot, or a fan is acceptable on the 36mm model.
Tim