I think there are a few things that float around worth discussing specific to this thread:
1.) Is there such a thing as undermodified malt? I’m going to say no. When I said you would have to really look hard to find it, I think I was being charitable. I don’t think you can find a truly undermodified malt in the homebrew market.
2.) The idea that you should mash based on beer style, beer country, etc. is bunk. You mash malt, not style. Mash schedules are and should be tailored to the malt being used. By extension, you should try and familiarize yourself with the base malt you use. That’s actually easier said than done because for the most part, Weyermann is really one of the only maltsters out there who makes it easy to get data sheets.
3.) Should you step mash? Maybe, maybe not. I’ve always had a specific reason to do it. I brew mainly Trappist inspired ales. I also brew small batches. Why should anyone care about that? Mainly because it informs you about why step mashing benefits me. I want the maximum amount of highly attenuative wort I can get because my style I brew demands high attenuation and my small vessels often limit the amount of first wort I can get because I no sparge. I want to ensure through multiple beta rests and a long alpha rest that I get 100% conversion efficiency.
That’s just me. The big thing to take away is that step mashing is not a flavor component. Multiple rests can help with fermentability, extract, body, foam and overall wort quality. Do you need to do it? Absolutely not if you are happy with the product you get using single infusion. But if you start asking yourself questions that lead you down the road to step mashing, you should entertain that certain aspects of the wort you produce, and ultimately the final product you drink, could be enhanced by investigating the benefits of different mash regimens.