Say there's a job opening CPL only required. You apply as does somebody with a frozen ATPL.
This guy is further qualified than you in terms of theory exams and practicality. You might get the job but you'll be competing with a lot of unemployed people who are further qualified than yourself.
Or say you have your CPL and then Jet2 start hiring low hour guys, only requirement is frozen ATPL. You've missed out.
Be fully trained, fully ready and then you can pounce on the first opportunity that comes.
But as always, it depends on you, your situation, want you want and how you want to do it. Many ways to skin a cat.