No, and might have?
I had purchased four similar models (ones that didn't have to lay horizontal) for a re-plumbing job on a four plex. I wanted to split the city's metering for each unit. (The city wanted $20K EACH for that!!) So I didn't bother too much about accuracy. Truth be told, I didn't even think to look into it, I just assumed it, and as it turns out I didn't need to: I use them to calculate what percentage of the city's meter to charge each tenant, so inaccuracy isn't really an issue. It's close enough for what I'm using them for.
Anywho, I just happened to be doing that project, so had the meters laying around, right when the pool was getting remodeled. I attached one to a garden hose and filled my pool with it. Much higher rate than .25GPM, so my volume number should be good. (Confirmed with testing and dosing.)
I really like having a good number, so I started "selling" the idea here (buying a meter and putting it on a hose), and selected the model I shared with you as "good enough" for this purpose, pretty much the cheapest Flows sells. But there have not been many takers. I later refined the idea to make use of a house's built in water meter, with tips about how to compensate for in-house use while the pool was being filled. That idea got some traction here because it's free! Not that I invented the concept, I'm sure others figured it out, too, well before I did. I just started sharing the idea for new builds and remodels, especially with free-form shapes, because they are really difficult to calculate based on dimensions.
According to this datasheet:
http://s144276.gridserver.com/wp-content/uploads/2012/03/poolmiser_ins_sheet.pdf
my autofill can deliver 4000 gallons in 24 hours, so that's 2.77GPM. But it's not clear if that spec means it would deliver water at that rate for each "mini-fill" or if the nature of auto-filling, little sips as the water dips, would mean it would mess with a water meter's accuracy.
I seem to notice that my water level drops by as much as about 1/2". That says to me that the float on the auto-filler allows the level to get low enough before it engages to then re-fill at that 2.77GPM rate, but I've never tested that to confirm. I thought about buying a dedicated meter to keep track of evaporation, but then abandoned that idea because it'd be about an $80 expense, and I'd have to dig up my line a second time to plumb it in. I figured if I needed to know that bad, I could just do what I recommend to others, and use the city's meter for a few random days throughout the summer months to calculate what a typical hot day uses up. But I'm too lazy for that. It is what it is and knowing what it is wouldn't lower the water bill any!! It's a fixed expense, nothing to be done about it (because I don't cover my pool and wouldn't want to). Part of me doesn't want to know!