Existing remote modules are essentially “grandfathered in” from their inclusion as such in older VTK versions (pre-9.0). For various reasons, pre-9.0 VTK did not provide a suitable environment for wrapping VTK code from VTK’s install tree. This has been resolved since then.
So, the bar is pretty high for this. What benefits are available by making it a remote module. Note the downsides:
lack of control on the code when making changes (VTK tracks it by hash, so any changes VTK makes that require updates means making PRs elsewhere)
for the above reason, CI does not use remote modules
ends up requiring the network for packaging from source tarballs (as remote modules are not in the source tarball)