They do appear to work as designed in that the G4M2e will launch the Ohka from outside enemy AA range and the Ohka can hit a naval target (and do a lot of damage).
As bbbf pointed out though, their use is dependent upon the availability of sufficient Ohkas in the relevent industry pool. At a rate of 9 Ohkas a month being produced, you can't really make use of more than one G4M2e air unit in play at any one time (and even one is a stretch).
You can alter the number of Ohkas being produced through the editor. The Japanese produced around 750 Ohka 11s from Sept '44 to March '45 so I normally change the monthly production to around 90 Ohkas prior to playing a scenario (I always wondered whether the monthly rate was mistakenly set up as 9 instead of 90 in the first place).
I can believe your claim about the test strike numbers as there appears to be a minimum number of strike aircraft per G4M2e air unit that will continue to fly Ohka missions even when there aren't enough Ohkas in the pool to fully support a strike of that size.
The situation I saw in a recent game had 6-10 G4M2es (out of about 50 available) flying daily strikes with Ohkas even though there were only 2 Ohkas available in the pool each day. Prior to that (when there were more than 50 Ohkas available), I was able to get all 50 G4M2es flying on the strike. As the numbers of available Ohkas dropped (below 50), so did the number of G4M2es taking part in the strike. This drop continued until the "minimum" was reached.
It seemed apparent to me that the number of G4M2es that will take part in a strike is very much related to the number of Ohkas in the pool. So any mass upgrade to G4M2es is probably counter-productive unless you have very large numbers of Ohkas available.
As to an Ohka hitting a target, it happens. They don't appear to be very accurate but I've still seen it on various occasions in stock games, both for a human player and for the AI. However, I can't recall whether or not I've seen an Ohka hit a target during one of these "minimum" strikes. It could mean there is a problem there or it could simply be that the air units that I saw launching Ohkas under those conditions had woeful experience levels.