Yeah that's in the "resources" tab. When people spawn units with moesbar hack (or at least with some version of the hack) the units are added in the free units stat. That's basically a stat that usually sums up all units (not only military, all kind of unit) shipped, units from treasures, as well as, I think, all units granted from a tech (consulate unit techs, big buttons, minutemen, age up rewards...). So essentially every unit that wasn't directly trained.
I'm just not exactly sure how it works, for example: does the age up tc wagon from brits count as a free unit? Do the warchief pets count? But usually, it gives you a rough approximation of how many units your opponent shipped, which you can compare with how many he could possibly ship. I've actually got a good example for this:
The guy had 80 free units in colonial as france (I still had aoe in french at that point, but it's the last column on the right). You can usually get 24 max (3cdbs + 4cdbs + 8bows + 3huss + 6mm). You can round that up to, say, 30, in case there were some free unit treasures. But with 80, you're 100% sure he was spawning units. I had 18, so probably 3 + 4 cdbs + 3 huss + 8 bows.
The same works with "free resources" btw, I'm not sure exactly how it's counted but I'm guess it's basically all the crates you shipped/got from age ups/got from techs, as well as the starting crates. So if the guy spawned like, say, 5k worth of crates, you should easily spot it thanks to that stat, adding up all the crates from his deck + crates from the age up and comparing. Here we both had 2400 free res, which probably means 600 starting res + 400w age up + 700w + 700g shipments.
One thing though: it's fucked up for russia and china I think, it just inflates free units like crazy and then it looks like the guy was cheating.