In my personal experience in engineering related conferences, this is quite common. I would even say that high-quality conferences might do this more often.
This may emerge from the following reasons: Initially, some people submit high-quality papers, perhaps over several years, thus, they get known to be specialists in their field.
As the conference grows or loses some of its reviewers, a need for new reviewers is created. So, who do you ask? Some random guy you do not know well, or a specialist that has published for years on this conference?
So the specialist becomes a reviewer but, of course, will not stop researching and is still allowed to submit papers.
Thereby, reviewers often have own submissions to a conference. There might be a little conflict of interest as always, if you review work of potential competitors, but: There are several reviewers, so an unqualified "strong reject, I do not like this paper" will hopefully not succeed. Furthermore, rejecting a few out of dozens up to hundreds of submitted papers will not increase your chances significantly. You could even hurt yourself: If you reject all papers in your field of research, the conference might not be able to assign your paper to an adequate session and it might be regarded as off-topic.
I would not see the request for review after submission as something bad, it is quite the opposite: The organizers have really thought about who can review those papers with the necessary background knowledge. Personally, I hate it if someone without a basic understanding of my research tries to review my paper - and I also hate it if I am assigned papers that are clearly out of my field of research.
Thus, YES it looks ok, but be careful as always.