OP did not market it as universal, they explicitly say it is an iOS app in the description of the Show HN and on the website.

Honestly, your initial comment comes off as whiny and entitled: you lost maybe 30 seconds of your time clicking through to something that wasn't relevant to you, and there's "no excuse" for leaving a drive-by comment attacking the author for their choice of tech stack for a side project just because of that tiny inconvenience.