At the moment, there is no strong need for reproducible PureOS builds, because most packages are synced from Debian directly and are not rebuilt for PureOS. So, you can easily verify the binaries with the data generated by Debian’s reproducible builds project.
We will switch to full rebuilds eventually though, and when that happened, a reproducible builds project makes sense and it is likely that we will add this service to PureOS then (but even then we can not give an ETA for that, because such an effort demands both infrastructure as well as manpower, and that has to be sorted out first).
So, tl;dr: At the moment, reproducible builds aren’t super-relevant (only for PureOS specific packages), but in future there is a high chance we’ll have them. It’s on our long-term roadmap.