Perhaps logically it could be argued that free verse is a metric form in the sense that it's form is defined in terms of the absence of metre, it's the null case

But I doubt that's what they were thinking, more likely the person writing the blurb wasn't a poet.
I think the 'record' they're claiming has to do with the length of the poems in that competition, since the poets were asked to rewrite Burns'
Tam O' Shanter: On
the page for that competition they state: "Nearly 80 contributions were received of over 300 pages, making the competition a candidate for the Guinness book of records. The winners and all contributions were published on Facebook." But that claim doesn't make too much sense either, I guess.
You can find the winners of the Tam O' Shanter competition here on
Facebook. I had a quick look, I wouldn't say the quality struck me as great, but those are long poems; that's an awful lot of rhyming couplets -- and as I say, I only had a quick look at a couple.
Anyway, at least there are six prizes ranging from £25 to £300, and they seem to have a reasonable set of judges.