Safari: web app audio doesn't play in the background

I'd like to add short cuts (web apps) to my homescreen of a few radio stations. When I play the stream in mobile Safari (before making it a web app), the audio will keep on playing when I switch out of Safari. However, after I make a web app of it the audio will stop playing when I switch out of it. Is this how it is supposed to behave or can I fix this? Many thanks.

Note: these radio stations do have their iOS apps but I prefer to use web apps as much as possible, to reduce tracking etc.