Starting a fresh Pharo 14 image with an init script results in a debugger opening up.
Apparently the image is invoked using eval + the script name. In Pharo 13 this evaluates the script, in Pharo 14 it tries to evaluate the path name as pharo code, resulting in an error.
Both Pharo 13 and 14 support the st command line handler which seems to be the intended method to run scripts.