That surprises me!?? I know all these reports claiming, that only operational types were displayed, but following the demonstrator's maiden flight in 2013 we haven't seen this UCAV anywhere, not at its facility, not at Malan nor any other PLAAF base related to UAV & UCAs. So at least IMO I'm very much skeptical ...
I was surprised as well that it was shown at the parade.
I think its presence at the parade supersedes the fact that we've been kept in the dark about its prior development.
I.e.: the PLA are willing to tell to the world that they have such a platform in service in some form, but are being very careful about revealing details of its development or in service status.
Between the initial pictures of its photos back in 2013, and then the complete lack of pictures for 4-5 years with only some rumours of an improved variant being developed and tested, and then in 2019 being revealed at the parade, I think the takeaway is that it was likely developed as something close to the PLA's equivalent of a black project.
The alternative is that Lijian wasn't in development and isn't in service in any form, yet the PLA still chose to display it at the national day parade -- which IMO is far far more unlikely than the above suggestion.