I don't really think that questions like this one (as understood by this comment) are really answerable without simply saying, "Some people do one thing and others do another thing." I would say that such questions shouldn't be allowed here. It seems like this would open up questions like "Why do some ba'alei tefila start reciting out loud at 'borei yom valaila' and others start at 'uma'avir yom umeivi laila'?" and an unlimited number of other questions all asking about why some chazanim start reciting out loud in one place, and others start in another place.
There are infinite distinctions between one person's religious observance and another's that someone might see and be curious about. Most of them are trivial or otherwise not motivated by Judaism, but some of them are meaningful. This is definitely true with respect to which parts chazzanim say aloud, as indicated by the answers to these two questions:
Clearly, some of these choices are trivial, while some are meaningful, and determining which is which can be a worthwhile endeavor.
Now, as always, the more information an asker puts into the question post about why this particular distinction is worthy of curiosity, the better, and the more worthy of up-votes. However, I think that a motivation of "I've seen this religious practice done two different ways; why the distinction?" is sufficient to avert closure.
(In the case of the question you linked to, the author made a case in the comments for this particular practice being not consistent with the form followed by similar prayers, which I think makes the question pretty strong.)