I would not say that it is difficult (especially in a year like this where we have had consistent cold but not freezes), just that the laws of probability come into play. In the warmer parts of the state they can't guarantee 1 cold front a week. In the colder parts of the state, there is also the chance that you may lose your flush to a freeze (just as happened to our swethearts 2 years ago). The trees that were still dormant at the time were unaffected and went on to bloom normally. Also, in a situation like you were in where the tree was flushing at the wrong time, there is nothing to lose by pruning. Pruning also has the benefit of putting the whole tree on the same cycle (rather than a mixed flush and bloom like your pic from the botanical garden). If you get bloom its pretty much all bloom; if its growth it will all be growth.