What is wrong with stating your preferences or requirements? It might result in someone making "better" choices and making more people happy. For example by using cross platform tools or building a web app, or releasing the sources (sounds in this case) so someone else can build something better.
They only said that an android version would be cool.
And I'm just saying that using cross platform tools has the potential to make more people happy.
Besides. They weren't just making an app for themselves, because it is in the app store (something which requires more effort).
Your comment is not grounded in reality.
> They weren't just making an app for themselves, because it is in the app store
"It’s something I built for myself first, but I figured others might find it useful too."
Let someone make things for the sake of it, and share that thing because they want to. Because it brings them joy. Without asking for more because you would make different choices. I urge you to self-reflect on what led you to the comments you are making.
Nobody is forcing anyone to make different choices.
This is a forum, where people discuss things and make suggestions.
If some suggestions rub you the wrong way, then maybe take some distance and don't try to take it as a personal attack. Because that is totally not the intention here.
I don't see anything wrong with someone suggesting similar apps on Android or being disappointed they can't use this because they don't use the same OS as the author.
Comments suggesting an iOS developer who made a free iOS app for his own use and then shared it should go and make them an Android app can only be described as entitled ###holes.
Why didn't the author use cross platform tools? They weren't making a cross platform app. They did not need those tools. It wouldn't be "better" if they did, it would be unrelated to the requirements the author had for the project.