Windows and trim caulking, who does it? painter or installer?

[Tony Ngo]

Working on my first flip.  I'm having a general contractor doing all the work except for paint.  It's an extensive rehab project where we're replace all windows and interior doors.  We're putting new trims and baseboards.  My GC says the paint guy is supposed to caulk before he paints.  The paint guy says he doesn't caulk because the paint would crack up.  I'm not sure how to approach this.  I believe caulking is needed.  How would I go about this?  Is this normally part of a painter's job?  or is it the job of the windows'/trims' installer job? 

Thanks in advance for your input!