Some folks might see it as useless others may see it as a great feature.
I'm one that hated the feature at first and struggled to get any battery to read over 60 until I figured out / understood what it is good for.
My P3 came with the small base cap spring, after replacement IQ went up 5ish, which was disappointing.
I have 2 old AW's that would read in the 30's & 2 brand new AW's that read 50 ~ 60.
My vtc4's & one surviving vtc5, samsung 25r & 20r, AW 18490's & a few other brands all had similar IQ readings.
I cleaned every threaded surface, every battery contact point, the 510 pin & threads, where the spring seats against the base cap with rubbing alchol & noalox using a tooth pic, safety pin a bunch of cloth & paper towels & napkins.
The IQ went up by 10ish, a week later I re cleaned everything and the IQ went up another 5ish.
About two weeks later I cleaned everything again and used no-ox, IQ went up again, next cleaning even the old AW's read mid 70s to low 80s, the new ones read high 80's to as high as 97.
I have & use all sorts of batteries, there are some my P3 IQ just doesn't like no matter what I do.
The IQ on mine functions perfectly now.
Garbage feature? not at all in my opinion.
For someone like me that uses vape stuff in severe conditions it is a great feature to let me know when it is time to service / maintain / clean and IMO it certainly works to determine the quality / life stage of the battery.
This aint no fanboy post, I was beyond ...... that I had to clean a brand new device so many times & so thoroughly and replace the spring base cap to get it to function properly.
For the cost of the device and in today's cheap APV market they need to ensure all threaded surfaces are cleaned spotless until they glisten, all battery contact points & 510 pin cleaned until they shine and put a battery in each unit & test to ensure everything is 100% before they ship one out.