It's not a clear-cut as this.
Once the order is of a size substantial enough to fill a kiln, any maltster (WEY or BEST etc...) are willing to produce the malt according to your own specification.
The problem for large scale operations is that storage translates directly into overheads. Therefore a restriction of ingredients to be kept on site is on order.
For e.g. Augustiner-Braeu has their own (floor) maltings for their Helles malt, yet they are a customer of BEST. That's quite telling really.
So if you go there and ask them, they'll tell you that they have only Helles malt in their silos. However, they produce some pretty nice Dunkel as well
Not hard to figure out what is going on.
Summa sumarum: What an outfit like Ayinger or Augustiner does in terms of the superficially perceived operations may not reflect the reality of production.
So beware before jumping to conclusions too early and potentially jump down the rabbit-hole.
My aim is not to clone their products. My aim is to be inspired by them, discover and learn what makes them what I like and then produce whatever suits me according to my own spec.
Isn't this worthwhile?