They’re not the same, but they are similar. I remember going from an OTK seat to an NEK, same as Jecko, before I got my new (good) rib vest.
The difference was crazy. I went from feeling pressure all over my back, to the point where practice sessions rarely lasted longer than 8 laps or so before it was so bad I couldn’t focus. To being able to run for what felt like forever with no issues or focus problems.
To compound this, the DR that the NEK was on had a KA bolted on, first time I had ever driven one. Going from a Yamaha Can to KA, I expected the issues to compound even quicker.
So, I wouldn’t consider the NEK and Jecko to be at the same scale as Deepseat or Ribtect, but it is a step above a standard Tillet or similar brand. I wouldn’t use one on my kart personally, I don’t think it flexes the same way as a “standard” seat, but it is noticeably more comfortable/easier on the body.