Summer is when they do maintenance and modifications to holes etc.
I've seen that flyover as well as photos and the course itself is left in a pretty untidy look. Nothing like what we see on tv in April.
Not 100 % sure what strains of grasses they use but would say that it's bent grass on the greens and in summer Bermuda and in Fall overseesed with Rye grass and grow and thicken it all winter.
The summer Bermuda grass withstands intense heat but goes dormant in winter. The Rye grass grown in fall and over winter is why it's so green and lush when we see it in spring. They also paint any areas of brown grass with green paint....noticed this when there.