Zoom tool no longer draws a marquee when scrubby-zoom is disabled. Every other tool that selects or otherwise covers a 2D area does... So this is a regression, and it negatively impacts performance and usability.
Maybe it's an el cap thing. I just tried it again. It does indeed draw the marquee about 1.5 seconds after I stop dragging if I keep the mouse still and don't release the mouse button first. Selection marquees draw instantly.
PS 2015.0.1 Release 20150722.r.168 x64
OS X 10.11.1 (15B17c)
Mid 2014 15" rMBP GeForce GT 750M