This is correct, it's a bad time of year for seedlings to grow but not a lot you can do about it other than trying to keep it damp, which is like trying to keep sand in a sieve. It will explode on you next spring though. Even some of the seedlings that aren't sprouting this summer will come up.
It's also notable to mention that as it warms up, grass nearly stops growing. I was mowing at least once a week up to June and have only mowed twice since, so the growth rate slows down a lot. Patience is also an important ingredient. :-)