Hi there,
Yes, it is the way the ports are opened and close in the mac stuff. it’s always been hit or miss. Works like a dream on a WIN10 box btw…
Have you tried setting the comm port manually to 1200 baud?
Usually you only need BL mode if your code upload was WACK i.e. bad, or switching BSP’s will do it sometimes.
Try this ; Upload a Basic code Like a Blinky and see if it improves after it uploads and you see it running… on Windows and Arduino IDE 2.2.3 once a successful upload and reset , It usually will work without pressing any buttons (or require BL Mode) the next times after. YMMV
It’s not on all MAC’s which is nuts too!
HTH
GL 
PJ 