If I understand you correctly, you're using YouTube in a browser on your phone. SponsorBlock only works on your phone because you've installed an "app": a browser extension that implements it within the browser.

Most people don't do this.

More people ought to do this. It's the best way right now to defeat spurious decisions by platforms. Reddit's app is off my phone. I use its terrible website, so I don't go there anymore. Youtube has a good website, and until they enshittify it, it's the best way to experience Youtube on a phone.

I totally agree: using the website (through Firefox + uBo) is generally the best way, because the user has the most control. A proprietary app doesn't give you this.