I'm going to assume your question is geared towards high altitude (20,000+ ft) climbing. Haven't done any myself but this topic is covered at length in almost every book written regarding Everest and the other 25k peaks.
Is this style of complicated looking height progression done nowadays
A common mantra for high-altitude acclimatization is "climb high, sleep low". A modern graph of a typical climber on Everest would follow a similar pattern, yes. The amount of oxygen in the air decreases as you climb up. Sleeping lower than you've climbed is the best way for your body to recover from the shock of taking in less oxygen during the stress of the ascent. During the night you'll be inhaling a greater percent of oxygen than during the day. It's similar to exercise training using heart rate intervals.
If so, is it done due to acclimatization?
Primarily due to acclimatization, yes. To a lesser extent, it is used to fix ropes and stash gear (oxygen, fuel, food, sleeping accommodations).
How did acclimatization strategies change over the last decades in
Not much. "Climb high, sleep low" fundamentally hasn't changed. Its the most scientifically proven acclimatization strategy. There isnt much agreement as to why some acclimate better than others from a genetic or preparation standpoint for most of the population living at <5000 ft. There are some medications which will alleviate the symptoms of high altitude sickness, but in a sense they dont really acclimate you any better. I've also read about some sleeping in a hyperbaric chamber.
Buhl is considered a forbearer of modern "alpine style" climbing, in his day norm for climbing 25k+ peaks was to "siege" the mountain with an over-abundance of porters, gear, and camps, gradually establishing camps up the mountain. This typically took several months. "Alpine style" climbing took over in the 70s, led by Reinhold Messner. The general idea is to climb light and fast, establishing less camps and minimizing the time spent above base camp. It's certainly possible that an elite modern climber could progress straight up - but many expeditions now are guide/client (especially on Everest) and in these cases they normally have 3-5 camps above base.
A good overview of altitude sickness and best practices to acclimate can be found on Princeton's website.
Finally, +1 on the graph.