Actually that looks quite interesting. I note that they make them 3 and 5 row too (possibly others?). One of the many related ads shows the bushing options and quite a simple idea but possibly a bit of a pain to change sets of those (hard to guess but likely have to pull the axle shaft out). Of course it doesn't appear to cover the seed and Id guess that planting depth relies on the operator angling it reliably so needs a very even seed bed - Happy to be proven wrong. Cheap enough for a punt if that sort of seed concentration wanted (as in growing some grain or a moderate plot of onions, radish etc). I'd also hazard a guess that one could buya 5-row jobbie and remove some hoppers to adjust spacing if one enquired?
Sadly of no use for me - I'm giving up the heavy weeding and reducing my growing further this year.