To.
I would like to know if there is really so much of a difference between the Ajax-Barca-Bielsa school of high pressing football, and the Gegenpress-Red Bull approach.
Football admin seem to think that they are commentary from the way Leeds hired a Ragnick disciple to take over from Girls a, and Manure probably figured that stylistic similarity was important in bringing Ten Haag to replace Ragnick.
There is a difference.
Gang pressing is something that’s been around for ages going back to the Kiev team of the 70s probably (and perhaps some earlier iterations as well), while the Cruyff teams of the 70s are probably the blueprint that kicked off the possession-based total-football approach (although you could argue the Hungary team of the 50s and a few others did it before them).
Ultimately they both involve getting the ball back from the opposition or keeping it from them, but a high gang press German team is at its peak when it wins the ball higher up the pitch and goes with the concept that the team that has just lost the ball is at its weakest state defensively, with players likely out of position. So there is an emphasis on attacking quickly before the opposition recovers its shape.
The total football style of play is inherently different and has emphasis on breaking down opposition defenses. This is done firstly by players interchanging positions, while maintaining a general shape in attack - so this requires players to have very good technical skills on the ball so you'd typically see defenders who can play in midfield, or wingers who play as strikers, etc. The modern variant involves everyone being comfortable on the ball to also beat a press and use the skills of players to get ahead of the press where they'll potentially find spaces to exploit.
It's interesting that you mention Bielsa because him and Marsch kind of have different approaches. While they both involve pressing there is a difference in the way they press as well. Bielsa's pressing style is focused on man marking and being a step or two ahead of the game so it involves more sudden acceleration from his players and they'd have to change direction a lot to stay ahead of the opposition. Marsch has his team working just as hard as Bielsa, but with him it is less about marking and some emphasis placed on positioning and shape, particularly in the middle of the park. So if a player they are trying to press moves out of range, someone else takes over and the player doing the pressing reverts to position.
When you dive more into it, pressing itself is different and different teams have different goals. With RBL, their press involves pushing the ball out to opposition fullbacks and immediately closing the passing lines and attacking the fullback with some intensity. So their goal is to win the ball off the fullback and immediately cut in and you'd often be running into space with only a CB ahead of you. Simeone has his deep press where they concede the flanks to the opposition and win the ball deeper and centrally. Bielsa goes with his crazy man-marking approach. Marsch has his gang press with positioning fixed. Etc. etc.
Moving on to Ten Hag, he's in the new school where you combine the approaches of pressing and positioning play so that you attack and defend in different ways to adhere to different situations. For example, his Ajax team could build out from the back and play a more patient tiki-taka style at times, but they could also go more direct with quicker transitions if there were spaces to exploit. Also they could press high, but also hold shape depending on the situation. The problem he's facing right now though is that his style takes time in terms of players understanding what to do depending on match situations and also players having the right skills. His philosophy is to make use of the skills that players already have, but that's difficult with this current United side since they are a mishmash of players with different skillsets to fit a multitude of philosophies and who have played under a variety of different tactics. At Ajax, they had players who are groomed from academy level to play in a certain way, and the style of play of the players they sign normally fit into comparable tactics and approaches. He doesn't have this luxury at United and the pressure is high as well to get immediate results. It's a tough job in my view but he can do it if he gets time with some acceptance of failure and if he gets the right players in.