Practically, all laptops feature the x8 lane limit to the GPU, for a few reasons;
- most mobile GPUs don't have all 16 lanes present, to save power
- mobile CPU parts only have 20-24 lanes total... because more wastes cost and... power
- using a chipset with more lanes (or at all for AMD laptops) increases costs... and power again
- the 2080 and up are the only GPUs really that would actually take advantage of the full 16 lanes, of which at that point you're going to be CPU and GPU TDP bound anyway... because power
The ryzen 4000 mobile parts already have 20/24 lanes present. No, you really don't need any more, and no, you don't need a chipset there to boost the lane count. If any manufacturer really really really wanted their laptop to feature a x16 link to the dedicated GPU, they'd simply not wire the second NVMe slot, or split the second slot to only x2 lanes.