Safari 26 brings a smoother, more app-like feel to many websites on iPhone and...

https://bizzmarkblog.com/why-does-my-ipad-web-app-feel-different-from-the-same-site-in-safari-tabs/

Safari 26 brings a smoother, more app-like feel to many websites on iPhone and iPad. When you add a site to your Home Screen, it now behaves more like a native app with fewer browser elements visible