The list is including all sorts of nonsense as grunge, like alt rock and garage rock. Grunge was a subgenre of alt rock, that doesn't mean that all alt rock was grunge.
Barely any grunge bands are listed as still active on that list you posted, and those that are include stuff like Soundgarden, Smashing Pumpkins, and Pearl Jam who haven't been anything resembling grunge since the late 90's (and Soundgarden reinvented itself after a 13 year breakup - they're just a rock band now).
A cursory glance at the articles of ones listed as still active also shows things like "got back together in 2015 for one show". One show every few years does not an active band make.
It's a Wikipedia list so I can't say I'm very surprised, but I am disappointed that you obviously didn't even look at the list before posting it.
Here's a breakdown:
Bands listed as active:
Alice in Chains - always said they weren't grunge, got lumped in. Haven't released anything resembling grunge since 1995, and their new album was a deliberate step away from their 18 year old sound)
Girl Trouble - Garage band (not grunge) that have been thoroughly unknown since they were formed
Local H - Actually a still existing grunge band
Love Battery - Haven't put out any new material for nearly 20 years
Malfunkshun - Actually a still existing grunge band, though they basically put out their first album and sat on it for over 15 years
Marytree - Grungemetal isn't grunge
Melvins - Started as a punk band, got famous cause they were close to Seattle. Never a grunge band
Mudhoney - All grunge is alt rock, alt rock is not all grunge
Napalm Beach - Are a punk band for god's sake, not grunge
Pearl Jam - Were definitely grunge, are now a rock band
Seaweed - More punk than grunge, famous because they were close to Seattle
Smashing Pumpkins - Good god no, not a grunge band
Soundgarden - Were a grunge band in the 90s, haven't been a grunge band since their 2010 release
Sweet Water - Rock band, not a grunge band
Toadies - Alt rock isn't all grunge
Truly - Super obscure band, but agani not all alt rock is grunge just because grunge is a subgenre of alt rock