It does not clear all private data

Shortcut tiles can be either pinned (you've added those manually so you'd need to remove these manually as well), or are the most frequent/recent sites from your history. Removing site data does not change your history itself.

Have you deleted all your history as well?

I have disabled Shortcuts. Nothing is pinned. Deleted all the history. I have attached some screenshots for reference.

The screenshot shows you have nothing shown on the home tab if that's what you call "splash screen". The only other "splash screen" being a loading animation only has Firefox brand logo and no content.

Can you elaborate a bit more where exactly you see your previous content? Thanks!

I know that’s the Home tab. I didn’t call it the splash screen. I always close Firefox from memory. As soon as I reopen it, that’s where it briefly shows the previously opened website for just a second.

Could you record a video and upload it with a bug report to github.com/mozilla-mobile/firefox-ios/issues please?

I'm suspecting what you're seeing is a stale iOS–level app screen snapshot that's shown when the app is not active (yet), so any data captured there from earlier is in the hands of the device/OS at that point.

I think this is a stale iOS-level app screen snapshot. I’ve been testing this in Safari for the past week, and the same issue is happening there as well.

I do not know where the Apple bug stems from, but I once had a pre–iOS–update app screens cached in switcher and launcher posters for months before it eventually cleaned out (on a pretty new and quite powerful device, so it was not there was any memory pressure or slow launches etc.), stuck from before applying an update, all the way across several further updates (or, if it disappeared after a few weeks, it came back right with the next system update and started to trickle down from scratch again).

So I'd just advise to ignore it for a bit, to see if the launcher/switcher caches eventually rotate or purge, or get empty on your next major update perhaps — it should straighten out but it's outside of the individual apps' control mostly.