One of the things revealed in the firmware and documentation is how the HomePod will handle Siri queries. Basically it seems that Siri on the HomePod will be somewhat barebones, where it will be capable of handling music playback queries on the device itself. However anything more, it appears that it will send those queries to a linked iPhone or iPad instead for processing.
We suppose given that Apple seems to be positioning the HomePod as a device for music consumption, it makes sense that they would try to keep Siri music queries local to the device. Whether handing queries off to a separate device like a linked iPhone or iPad will cause any delays remains to be seen as the HomePod has yet to be officially released.
The HomePod is currently set for a release by the end of the year, but there have been reports to suggest that it could face some supply constraints at the start.