When you cut a branch/limb off it will contain reaction wood (either compression or tension) and it will have the pith but it is typically much more off center. Yes it will crack the same. You should try to cut through the pith so that the grain is balance; you may end up with one piece much larger than the other. Also be prepared for more drastic warping.
End grain turning is when the fibers or pith run parallel with the bed of the lathe, also called spindle orientation. Typically you are not cutting the end grain (boxes and some other items excluded) so it sounds a little backwards.
If the end grain is perpendicular to the bed (the way most bowls are) that is called face or bowl or blank turning. Maybe a few other terms also but those three are the most used.
Below is a picture of a pecan limb showing the pith way to one side. The pith was cut about 1:00 to 7:00 in the picture giving one small and one large blank but the grain was as balanced as possible. You can see the pith was at the very side of the heartwood also.
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