3in1 grass seed

[cut-n-care lawn care]

I have a question about 3 in 1 seed (seed,mulch,fert.).I recently did a couple of jobs where the customer wanted to reseed some bare spots and our growing season was coming to an end, so I reseeded with this type of seed witch was mostly made up of fescue and bluegrass .After I had done this another local
landscaper told me that is was a bad move because he had problems with 3 in 1 seed not coming back up in the spring and if you were to rake it the roots are not strong enough to hold and will pull out . Can anyone shed some light on this subject? Did I do the right thing ?If not any suggestions.

[Runner]

One of the most common mistakes people do (REAL frequent) is that they put this stuff on too heavy. For some reason, people think that this stuff is supposed to cover he area (like hydro-seeding). This isn't the case. It should be about 50% covered. Now, I'm not sure if this was the case or not, as it could have also been soil condition, care conditions (water, etc.), or a large number of other things. I can say that I have used it in the past, and it worked well. Personally, I prefer just a good seed and starter, but each their own. The mulch definitely helps to retain the moisture.