Hi Roberto - we'll need to run some checks on a Mac to see if there is some peculiarity related to that platform and get back to you.
I haven't been able to try this yet, but to eliminate it as a possibility (and to give you something to try in the meantime), could you please check/try this fix for a known issue with MacOS (from the IDE installation guide):
1.3.1 Mac OS X Sierra – Unexpected Delays during Debug Operations
Mac OS X Sierra installations may experience an approximately 5-second delay when a call to get the localhost address is made from Java. This call is used within MCUXpresso IDE
when establishing a debug connection for LinkServer, P&E or SEGGER. Therefore, if a delay is experienced during a debug operation, the following fix may be required.
First, launch a Terminal session and enter the command hostname, which will return something of
the form:
~$ hostname
user-Mac.local
Next, edit your /etc/hosts file and add the returned hostname after the localhost entries as shown
below:
127.0.0.1 localhost user-Mac.local
::1 localhost user-Mac.local
Save the etc/hosts file. Once this change has been made, the 5-second delay should be reduced to a few milliseconds. Further information about this issue can be obtained by performing a web search of the form MacOS Sierra Java localhost slow.