It's complete and utter horsecrap, also nothing to do with hindsight, aside from the fact it turns out Honda Japan has been struggling badly everywhere for years(I don't follow the industry at all but it seems all their engine programs are... meh) and they committed to a program that to me completely assured failure. Long before the start of the 2015 season I, someone with zero experience building engines, but a basic concept of common sense, time, and how these things work together, said that the idea of rushing a complex engine in 18 months when the other teams would have twice as long had disaster written all over it. Further after 2014 started and two of the three engines that had twice as long for development turned out to be disasters... it further reinforced my belief that 18 months development was going to fail badly.
I wish people wouldn't use the hindsight argument when simple common sense on day one of the announcement screamed terrible idea. I thought that straight away and I had no clue Honda were apparently struggling in most areas. It seems only Honda America has any decent engine programs going. Had I known that I would have only been further convinced this was going to happen.
Then back to the whole "can't win without a works engine" nonsense, of course Ron would say that, what else would he say. Somehow Williams got the fastest straight line car on the grid... despite not being a works team and having to build around an engine that was liable to change. The fact of the matter was with Honda with the program they outlined they COULDN'T win, with mercedes, who at the time were widely known to be putting the most money AND time into the new engines, they could be assured of being one of only two big budget teams with a Mercedes engine which conversely had the best chance to be dominant.
Are their disadvantages, sure, Merc will be 'first' to know about any changes, but a lot of fans act like Merc just turn up with an engine 2 weeks before the first test and everyone has to rush to fit it in. Merc have an advantage, though it would diminish drastically by the second year. IE the new engine is most liable to bigger changes in the first year it appears, after that the changes aren't going to be that massive. Mclaren also have 2-3 times the budget of Williams/FI, they were most ready to make small changes to the aero/covers/chassis to adapt to new changes.
If Mclaren could make a better chassis than Merc, they could absolutely beat them with a Merc engine, the problem was Ron didn't believe they could make a better chassis, he believed he HAD to have a better engine than Merc to beat Merc. He's probably right in that, but again for the reasons above it was obvious Honda was going to struggle massively to make any engine, let alone one better than Merc. With Merc they had a 98% chance for a top and competitive engine(not best, just competitive) and given the choice of a ridiculously rushed engine from Honda... who currently suck as an engine manufacturer and sticking with a Merc engine and replacing staff on the chassis/aero design side, there was an extremely obvious right and wrong choice... Ron made the wrong choice and Mclaren have been paying for that choice ever since and I think they'll be lucky to have a half decent engine by 2019 at this point.