There has been testing done with these products - at least the older type versions (think Hagen Cycle under various (new) names), including some by T Hovanec back when he developed his version and was still writing up scientific papers (and long before his affiliation with Tetra)
Conclusion - Dr H’s product “cycled” aquariums much more quickly, but even Hagen Cycle reduced the “cycle” time by 2-3 weeks (this was put down to ineffective bacteria solution acting as a nutrient source for the newly identified “cycling bacteria”)
TH signed a contract with a suitable company and his special bacteria solution was available for some years - unlike the competition, this version was kept chilled and had a shelf life of several months (if you were in the US you could also order it direct from the company)
It experienced considerable success among African Cichlid keepers (where all fish are usually best added in one go for best chance of a successful community or shoal (eg, Tropheus sp.))
I sort of lost track at this point ...
Enter the Newest Cycle Story - and the various papers linked by
@dw1305
Back to anecdotal “evidence” - Seachem Stability seems to work (proprietary ingredients but at least Dr Greg has the science ... though not sure how much control he retains as Seachem has become a commercial company in much the same way as the ADA story)
Note that like Dr H’s Original Stuff, Seachem Stability is also meant to be added WITH FISH - read through the Seachem FAQ page and loads of discussion on their Forum (which sadly looks to have been hacked again

)
though there are several shops etc that will recommend it be used in new aquariums with first livestock additions 4-5 weeks later ... again, anecdotally that seems to work alright too
I’m somewhat lost on that logic (again

)
If you want to “jumpstart” a “cycle” in your aquarium, add some plants/hardscape/gravel/media etc from a running aquarium
(I don't get the objective of adding soil bacteria - which is pretty much Hagen Cycle products anyway, but sans dust - but there are plenty of folk that will swear by this method too

.... and perhaps it works in much the same way as Hagen Cycle

)