It does seem like the Holdo maneuver’s look was based that storyboard, but I think it’s ultimately a misinterpretation of what was intended; the ROTJ scene is showing a Starcruiser exploding alongside a Stardestroyer, due to what I’d characterize as the Star-Wars-equivalent of Star Trek’s Warp Core Breach. The ship is so damaged its reactor goes critical or whatever. So they drew that picture to convey the intensity of the explosion, and decades later its used as inspiration for a very different event on screen.