Honda's failures as a team owner is inversely proportional to their success as an engine supplier.
I am sure that 20 engines would not have been too difficult, as I'm pretty sure that there were availabilities of left overs from the last 2 years, as well as the rest of Super Aguri's supply for 2008.
Maybe they wanted to remove themselves from the embarrassment of having their name on another loser, but to be honest, if Honda wanted to avoid embarassment, they would NOT have sold their team to the same people that were there already, and having them pick up a competitors engine, and then go on to score alot of points/win a few races.
That will only have the worlds motorsports headlines talking about how bad Honda really is as a management and engine building body.
Not good press when the car market is getting a bit cut throat.