I don't see much of a point in this since people are still working with non SegWit addresses, so the benefit isn't really there if ChipMixer does happen to roll it out. I can only see this being a viable option when people on a large scale are transacting with SegWit addresses, and as long as that isn't the case, it's not much of a useful addition. SegWit has been active on Litecoin for quite a while now, and a lot transactions there are still non SegWit, which basically means that people and services haven't yet taken the effort to actually utilize SegWit to the full.
If I remember correctly, the actual usage average a few days ago was somewhere around 15% and going down for whatever reason. Personally, I don't even know which wallets support the feature and which don't. Regardless, the number of transactions performed from ChipMixer addresses may be negligible to the total amount required for SegWit to significantly decrease transaction sizes, but if enough places were to adopt this feature, it would help the network significantly. If ChipMixer were to adopt this they could set an example, albeit it would certainly not have a direct effect on transaction fees.