If you were to read all the labels stating ingredients and quantities, in chick starter, chick finisher, and all flock feed such as Purina Flock Raiser, you would be astonished to see that they are all practically identical.
I discovered this several years ago as I stopped by the feed store to pick up a bag of chick starter for some new chicks that had just hatched. Curiosity made me compare labels with Flock Raiser. Yup! Identical.
Finisher may be a bit higher in protein because, guess why, fed to chicks over ten weeks old and you can get them grown out faster and EAT them!
I suggest you skip the "finisher" and just get a bag of all flock feed. You can feed this to a mixed flock of all ages and genders, including layers. Make life simple. Ignore the manufacturers suggestions. They want to sell product.