There are delegates who are forced by rule to vote for the pledged candidate on the 1st ballot. Those are “hard” delegates, and give the lowest counts.
However, there are also COMMITTED delegates, meaning delegates we already know are going to the convention, who were chosen by the candidates to run for the delegate slot, and were elected to support that candidate. While these delegates are not bound by LAW to support their candidate, it is highly unlikely that, barring death or other catastrophe, they would ever vote against their man.
BTW, in many cases the presidential electors to the electoral college are also not bound by law to vote for their candidate, but except in rare protests they all vote properly, simply because they are chosen to do so.
So, unless you believe that McCain chose trusted people for his delegates who would be likely to bolt for Huckabee simply because some conservatives whine about it, counting these delegates for McCain is not really an issue.
BTW, Mitt Romney seemed to win a preponderance of elections where the delegates were these soft-pledged delegates. That’s why he is more able than Huckabee would be to tell his delegates to vote for McCain. They don’t have to, but if they were committed enough to be in his inner circle, it is likely they will listen to his opinion on the matter.