I never heard of California style before, but perhaps it's because I started playing in California then migrated to Washington a year or so later?

From my experience, everyone used to play with a style very similar to what you call California Style. If someone got seriously into AAA'ing charts, then they generally shifted towards flat-footing (in the way I know it), or if they were trying to tackle incredibly fast, hard, and streamy charts, they'd begin to use the heel-to technique. Now that most "regular" players are beat-mode hardcore type, Heel-Toe is 90% of what you'll see. I still play in what you call the California Style, or flat foot style, but I can't do 12+ difficulty charts.

In short: Easier songs that require more body movement (generally no-bar play), will use the style in that G4 video you posted. If you're trying to 99%+ a 14, you're not going to get very far unless you heel-toe the f*ck out of it. That's why a lot of people are modding pads to make it easier to do the heel-toe technique.

Yeah, the DDR machine I played on back in 2007 didn't have the best maintained sensors, and even still, the dance pad wasn't designed to be heel-toed, since the screws holding in the arrows stuck up too far for your feet to lay flat across more than one arrow. So I didn't even really consider heel-toe style until I started looking into ITG. While I would often hit the down arrow with my heel on harder songs, it wasn't anything close to the actual heel-toe style... that's just the only way my foot could hit the down arrow when I was raping the bar trying to scrape through PSMO. I guess that'd be kinda a hybrid style where you're still hitting the arrows with enough force to register the steps even on a not very sensitive machine.

I remember back in 2010 (the last time I played DDR), I went to the ITG at TILT Llyod center. I didn't like a lot of the 11+ stepcharts on ITG. They felt kinda gimmicky to me (which partially had to do with my lack of heel-toe technique). I did really like Hardcore Symphony though, and I know I could pass that with the California/hybrid style if I had enough time to get in shape and learn the chart, but any of the other 12+ songs weren't really within my reach. I also love the song Utopia, but can't stand that stepchart. There were also a lot of songs on ITG1&2 that I liked but only had stepcharts up to 8 or 9 feet. Most of the 8-9s on ITG felt almost like standard difficulty on DDR to me.

It makes sense that most of the people still playing DDR are the hardcore players. I've seen some videos of people playing in the last few years and am blown away by what they can do, though I noticed that they've got better outfitted/modded pads to support the heel-toe style (like you were saying).