In the games industry I was tech lead of teams of hundreds of devs and had to deal with their estimates of this sort on a daily basis. 6-10 weeks for a total renderer rewrite is on the low end.
As an indie dev who built their own WASM-capable engine that I've shipped in real games, I've built both WebGL and WebGPU renderers from scratch myself in significantly less time than that. Sounds like typical corporate dysfunctionality. If you have hundreds of devs you're going to get bogged down by having a share who spend 90% of their time at the company on Reddit, another share who write actively bad code, and then maybe 10% of the employees who have a clue what they're doing dealing with the overhead of communication, meetings, other people not upholding their assigned responsibility, etc. slowing them down 10x what they could actually do.
As an indie dev who built their own WASM-capable engine that I've shipped in real games, I've built both WebGL and WebGPU renderers from scratch myself in significantly less time than that. Sounds like typical corporate dysfunctionality. If you have hundreds of devs you're going to get bogged down by having a share who spend 90% of their time at the company on Reddit, another share who write actively bad code, and then maybe 10% of the employees who have a clue what they're doing dealing with the overhead of communication, meetings, other people not upholding their assigned responsibility, etc. slowing them down 10x what they could actually do.