We have no such proof. Those chips have not been released. All we have are rumors.
Source?
Have you checked what is available on the market in terms of RAM capacities and did the math required for having 36 GB on 256 bit bus?
2, 4, 6, 8, 12 and 16 GB per 64 bit LPDDR5 6400 MHz modules.
Thats why you have 8, 16, 24 GB of RAM on 128 bit M2 MacBook Air/Mac Mini. Thats why you have 16 GB and 32 GB on 256 bit M2 Pro MacBook Pro/Mac Mini. Thats why you have 32, 64 and 96 GB on 512 bit M2 Max MacBook Pro/Mac Studio.
36 GB is possible only in 192 and 384 bit configuration, with what is available on the market.
48 GB is only possible on 384 and 768 bit bus, with what is available on the market.
Considering that Apple will increase the amount of CPU cores and GPU cores in upcoming M3 series, and their architectures are heavily memory bandwidth reliant - Its very unlikely that Apple will lower the memory bus width with next generation.
I knew that Apple would increase the RAM memory bus when the rumors came out about 36 GB M3 Pro in a MacBook Pro, but 48 GB of RAM in M3 Max sealed the deal for me, considering what is available on the market. We will see 50% uplift in memory bus with M3, M3 Pro and M3 Max.
And the lineup should look like this:
M3: 6P/4E, 192 bit bus, 12 GB RAM, 12 GPU cores.
M3 Pro: 8P/8E, 384 bit bus: 24 GB RAM, 24 GPU cores.
M3 Max: 12P/4E, 768 bit bus, 48 GB RAM, 48 GPU cores.