If the headphones are meant to be used with the phone, then the idea that the headphones are future-proofed because they have a 3.5mm jack is pretty meaningless if you can't connect them to the phone with that jack.
In 2023, most people who give two shits about running wired headphones are using a USB DAC, even if their phone has a 3.5mm socket as the onboard AD/DA chipset is usually mediocre and struggles to drive most high-end cans.
It’s simplicity I terms of construction and standard.
Here, the older standard (3.5mm jack) seems stronger (not an expert but an user opinion) and easier to source than usb c.
If you can't use thing A with thing B unless you also have thing C, to my mind that obviously reduces the expected lifetime of being able to use the combination, especially when thing C is a third party part.