Yes there was the possibility that his birth wasn't registered but if that had a been the case, he still would have known the names of his parents. My friend did apply to purchase his birth certificate only to be told that there was no birth recorded for him between the years 1870 and 1880 in Qld. So he was either born interstate or he wasn't born a Wakefield although he claimed to have been born in Queensland. The search continues.......
So Qld BDM do not have a birth registration for a Charles Henry WAKEFIELD between 1870 and 1880. Please don't expand that to mean anything other than Qld BDM did not find a birth in those names between those years. It could have been registered at the local office but not received at the Head office, it could be that the longhand writing was in a scribble and the surname has been 'mis-read' or it could be that the birth was registered in another surname or the given names were reversed, or that Charles was raised as Charles, but registered under a different name. There are many explanations. Simply put, to my way of thinking, when looking at 19th Century record keeping procedures, Adoption should not be the paramount explanation for lack of details about a person's parentage.
The information recorded on a marriage certificate in Queensland was based on the information transmitted to the Registrar General
by the clergy. I find it very unusual for the clergyman to have conducted a marriage in 1900 without noting on the civil registration the name of the parents of the groom. It had been the practice of Anglican clergy to record these details for decades and decades. In fact, it is possible to make the argument that the clergyman was not permitted to proceed with a marriage contract without first obtaining these details, or at least noting that those details were 'unknown' after making enquiries.
I think it is a flawed decision to decide that simply because the details are not listed on the marriage certificate issued by the Queensland BDM that the person was adopted and/or that he did not know ANY of the names of his parents.
Have you looked for WAKEFIELD as a surname in Rockhampton in 1875?

Or on Queensland Electoral Rolls from say 1896 (when Charles Henry may have turned 21 years of age, and therefore become eligible to enrol to vote) ...
JM