I wouldn't say that poker isn't gambling... I define gambling (properly) as risking money to win money. This is something that is present in many other jobs, as the one you listed shulenberger, stock trader on Wall Street.
Poker is a skill game in which you gamble.
The difficulty comes in when lay people use the term gambling within the context of a casino, especially "gamblers" to refer to the set of people who gamble in a casino - as opposed to the set of people who risk money to win money. That usage of the term, and blurring of the definition, bother me. I view poker being compared to someone playing slots, as the same as comparing a chess player to someone playing tic-tac-toe, and say "well they're both games". Yes, obviously they are, however one is astronomically more complex and difficult than the other such that they are not only not in the same league, but basically at opposite ends of the spectrum. (What spectrum you ask? The Game complexity one....
https://en.wikipedia.org/wiki/Game_complexity )
So I'm not arguing that poker isn't gambling. It is gambling! I'm arguing that it's a skillful form of gambling.
And (completely changing topics), if you have the option to break-up an event in to two separate events in order to more optimally manage your bankroll, it is always superior to do so. After all, you could always just keep the decision to let it ride and not sell more action between the two events. Yet, in the case of a big jump in difference of buyin (25k to 500k), you now have the option to more perfectly tailor these gambling decisions to your bankroll needs. In fact, it is obviously ALWAYS logically superior to break up 1 decision in to more decisions... as the group of decisions always includes within its set, the original decision, as well as more decisions that might be better.