Coming here after seeing the results of the PU survey, I have a question to all 7 people that voted to retest Virizion although this might not be the most appropriate place for it
Why? Wasn't Virizion one of the most insane pokemon this tier has seen? Sure the meta is very different compared to when Virizion was quickbanned but still...
TLDR: It's coverage being not-perfect-but-threatening and its non-nuclear attack stats??
I'm not one of those 7 that asked to retest it, and I am by no means the most qualified person to answer this, but here's my best take:
Back when Virizion was suspected (before its quickban), it was voted to stay in the tier. IIRC, two things kept it in check then: 4MSS and Talonflame. Virizion wanted to run SD/grass/Stone Edge/fighting/Zen and maybe stuff like Synthesis and Air Sash for longevity/opposing Virizion respectively. The interactions between it and Talonflame were neat and also helped keep Virizion in check, with Talonflame destroying Virizion, but Virizion being able to Stone Edge Talon on the switch.
Then Talonflame left, and that's (probably) why it was QB'd.
I'm assuming in a meta rampant with Jellicent, Regirock/Gigalith, Flying-types, Steels, and Poison types, people thought Virizion could be a solid wall breaker without being broken, since dropping a STAB opens weaknesses to Jelli or Steels, dropping slash lets opposing Virizion kill you, dropping stone edge lets flying types wall you, dropping zen opens you up to poisons, and dropping SD probably misses out on some sort of kill (i dont remember and I'm not calc-ing this, but there's probably a reason I remember SD on almost every set).
Personally, I don't think 4MSS is enough to keep Virizion balanced, but I see why some people *may* see it as retestable, especially with its 90/90 offences and the holes in its coverage.