Does that mean these "EMBEDDED OPTIONS" can be only defined at the beginning of the pattern and therefore don't offer anything extra over flags option?
Yes, this is how they behave. The most important difference is that:
column ~ 'regex' (i.e., the operator)
can only accept embedded switches since there is no place to write a formal flag like you can with the functions.
Though there is a case-insensitive operator as a usability feature the other modes lack any external operator support.
