No, it doesn't interfere with getting weather via ADS-B In (using your Stratux). For those without an ADS-B receiver, it would allow weather updates using the cellular data capabilities (if any) of the device they're running iFly on. (Let's not get into a discussion of the FCC rules regarding having your device using cellular voice/data while airborne. But I think we all realize that most pilots don't remember to, or bother to, or want to, put their device into Airplane Mode prior to flight -- and remember to take it out of that mode once the flight is over of course.)
Your WiFi on your tablet and phone are connected to Stratux, so it does you no good. But if you're running iFly on both devices, you could turn WiFi off on the phone, or otherwise make it so it doesn't auto-connect to the Stratux, and then it would use cellular data to stay up to date weather-wise. (Assuming you have a data plan, and assuming you're within range of a cell tower.)
I leave this option on all the time. If iFly is up and I'm connected to WiFi then it's staying up-to-date regarding weather. Once I hop in the plane and turn my master switch on, my tablet connects to my ADS-B In device and gets weather that way (once I'm up high enough to get an ADS-B ground tower signal). If for some reason my ADS-B In device fails, or I have an electrical system failure, or I'm out of range of an ADS-B tower, or I have an intergalactic alien ship close by, or..., then my tablet would presumably use its cellular data capability to stay up to date regarding weather (if within range of a cell tower and if that alien ship isn't interferring with that signal too -- damn aliens).