I don’t think you quite understand how the system works.
The chances of one of the large ATOs with say a dozen or so customers on a course (within a few weeks of completing) not having anyone suitable is extremely remote. They would have been consigned to the dustbin of history long ago.
On average perhaps up to 10%(?) are not going to make it first time. There is a very close relationship between the ATOs and their airline partners. What is discussed in private is a matter for conjecture, but you can expect honest discussions take place. In any event they would have access to all training files (with customers permission), and would interview them as well.
I can recall one very bright student (self funding) from BAe Prestwick in the late 1990s who scored over 95% in every CAA written exam, first time pass on the IRT, but struggled throughout the flying. Recommended ~ NO
Bottom line: just because you are issued with a CPL/IR does not mean in any shape or form a guarantee of employment.