In my experience, anything that I have had of Bill's which had 'Wild Cherry Round Up' in its background, tended towards rust. Unfortunately, it seemed that he used this as a foundation plant for many of his daylilies because of its form, because "round as a bagel" is his thing.
I have never grown this daylily, and the database doesn't rate it for rust, but if you look at the parentage, both of those are rust buckets, so it would not surprise me at all if WCRU were also a rust bucket. Because of this, I stopped buying any plants (from Bill or anyone else) that had that daylily lurking in the background.
Bill does have other introductions which don't have WCRU in the background. I've had 'Winning Note' for a great many years, and it never had a speck of rust until this year (no doubt because it is now right next to 'Because of You', which is something of a rust bucket thanks to
its two parents, 'Victorian Lace' and 'Make Believe Magic'). 'Winning Note' is such a good daylily, however, that it is worth dealing with a bit of rust on the plant. (I have seen much worse... and I did think until this past month that the plant was resistant.) I also have Bill's 'Sun Silk' and 'Golden Honey', which thus far have been rust free, and I am trying to reacquire his 'Impressionistic', which I lost. (Sad to say, but Bill seems to not keep his older introductions around for that long. Lose them, and you're out of luck, unless you can find someone else with the plant who is willing and able to share.)
I guess the moral of this all is to not get so fixated on whatever your daylily "thing" is (form, or colors/patterns, or size of flowers, or whatever) that you ignore plant health, and here is where ancestry research is beneficial (both for hybridizers and for buyers).
However.... if their customers don't care about rust because "they are spraying anyway", or because they live in cold winter climates, then there is little incentive for most hybridizers to go out of their way to address the issue of rust susceptibility.
