With a desktop app you can easily and quickly command-tab to it if you want to use it. In contrast with a web app it's often awkward and time consuming to find the window/tab of the web app you're running amongst your other browser windows/tabs.
I don't really treat cmd+tab and cmd+` very differently, sorry. On my OS, both work: I can alt-` to cycle through windows of same application and alt+tab to cycle through each individual window (grouped by application); maybe that's given me the habit of treating alt+` merely as a filter on alt+tab.
Oh! This is perhaps also why I get annoyed by cmd+tab on Macs!!
Next tme on mac try cmd+' to cycle between windows of the same app(although im not sure, because it really is muscle memory). Cmd tab cycles through wndow groups? Or does it cycle through each window?
Which wm on which os do you use? gnome kde or something else?
Chrome has that sorted already on android, where you can run up a site with a home screen link, different icon and separate listing in the task list. Given the work they've recently put in on full screen mode on desktop it looks like they're maybe a couple of versions away from having something similar on desktop
They're actively adding features. It's a little more complex than it used to be with the manifest, and needing a service worker and encryption for a lot of features, but it's all still there
I see three "nice to have" benefits: full keyboard, copy and paste text/links when you're browsing the web and sending images taken with a traditional camera. None of these are essential for sure and I for one prefer using my phone but sometimes it can be handy.
None in my [Mac]book. If you're running on OSX, open WhatsApp web on Safari, allow notification & pin the tab. Same outcome but resource efficient (compared to an Electron app).