https://www.techpowerup.com/303707/msi-announces-geforce-rtx-4090-suprim-x-classic-reuses-rtx-30-series-suprim-x-cooler
 
MSI quietly rolled out the GeForce RTX 4090 SUPRIM X Classic. Positioned alongside its air-cooled flagship graphics card, the RTX 4090 SUPRIM X, the new SUPRIM X Classic appears to be reusing the older version of MSI's SUPRIM X cooling solution that the company shipped with RTX 30-series "Ampere" graphics cards, such as the RTX 3090 Ti SUPRIM X. The older cooler should capable of handling the thermal loads of the RTX 4090, as it has much lower power-draw than the RTX 3090 Ti. This isn't the only "Classic" graphics card from MSI, with the company planning Radeon RX 7900 series Gaming X Classic graphics cards that reuse the Tri Frozr III cooling solution that the company used with its RX 6900 series Gaming X products. Besides the cooler and product-design there don't appear to be any other difference in specs for the SUPRIM X Classic compared to the RTX 4090 SUPRIM X.
 
I suppose this is a way to save the company money in manufacturing.