I think this might be something HP people were telling each other at the time while getting smacked around by Sun. The Sun machines were still ridiculously expensive and while common, I don't think they were the default. SGI Indies were also quite popular and the Pentium Pro quickly started eating the overpriced Unix workstation market. By 2000, I doubt there were that many SV startup developers sitting in front of a Sun box. There were piles of them in server rooms, of course.
This meant that code written on Sun that performed well performed poorly on HP-UX occasionally -- not because HP-UX was a worse platform, but because corner cases in architecture could bite you. On your tier1 development platform you tend to weed those issues out early.
I worked at HP during this time helping software vendors port to HP-UX. I also spent some time on the side compiling open source projects for fun on HP-UX and then pushing the required patches back to the project's owner.
Anyone remember Pointcast?! https://en.wikipedia.org/wiki/PointCast_(dotcom)
I was assigned to them briefly.