This may have been true back in the early 90's, but unfortunately not today. Not one of the pro card recipients from this past USA would be able to qualify for the Olympia in the open class if they presented the same physique. You can even use yourself as an example. You had a year off between turning pro, and I think the best you could do at the NOC was 11th. You took another year off, then managed 2nd in two shows, thus qualifying for the Olympia. Had you not jumped right in the first year, it's conceivable you could have won both shows.
This would be true as well if chicken breast, broccoli, and cardio were the means with which these guys would keep themselves lean. Knowing differently for the majority (as do you), I disagree here as well.
I'm a poor example, as I was (muscle wise) at pro level due to my many years on the circuit....It was coming in dry which was my issue....which no amount of time was going to fix....actually competing MORE often would lend to more experience of dialing it in for the last 24-48 hours.
That said...we talking specifically about the top 6 guys at the Olympia who need (IMO) to be on the circuit throught the year to lend some star power to the shows...not all of the shows, but 1-2 wouldn't hurt.
I can't think of one advantage to having the best BBers in the world NOT competing more often...