Was it just my imagination, or was the trail a whole lot less crowded than usual?
I haven't been to Whitney in a couple of years but I'll comment on my experience here around Reno, NV. It seems many more people have discovered hiking.
Often trailheads have more cars than ever before. Yesterday my wife took grandkids to Mt Rose Waterfall - she had never seen so many people on the trail. Recently at Galena Creek Park there was about 50 cars in the parking lot at Jones Creek trailhead.
Same here in San Diego, CA.
Hiking is far more popular than it was when I arrived here 25 years ago. That's a good thing. Open space is being valued and people are getting exercise. REI is packed each time I've visited. My city, Poway, is actively purchasing land to enable more public access to the surrounding natural areas.
That said, the parking lot at the Whitney Portal was expanded as couple of years ago, so more space is available. Also, the changes in the permitting process may have discouraged would-be hikers this year.