As BillJ and Tinfoilhat have pointed out, these examples are not appositives. CaGEL defines apposition as the construction with a specifying NP supplement where the appositive NP could be substituted for the whole supplementation yielding an entailment of the original(CaGEL p1357):
The first contestant, Lulu, was ushered onto stage.
Lulu was ushered onto stage.
Other examples given are:
The murderer, the man with the scar, will be arrested soon.
A university lecturer, Dr Brown, was arrested for the crime.
A surprise present, a bouquet of roses, was delivered to my door.
An entire genre, the comedy thriller, has been made obsolete by the invention of the mobile phone.
A Sevfert galaxv - a galaxy with a brilliant nucleus -usually has a massive red-shift.
The examples given are instead ascriptive NP supplements, CaGEL explains that these constructions do not qualify as apposition because the supplement cannot always be substituted for the whole construction in such a way as to yield an entailment of the original (CaGEL p1358).
An information systems specialist who set up his own mobile app
development company established Web Organic in 2019 and tapped
contacts in the industry for help.
The president of the United States waged a trade war against China.
A fan of Michael Jordan flew to the US to watch his match.
The above do not give the same interpretation as the originals unless we have some further information - who established Web Organic, which time period in history is under discussion, which fan of Michael Jordan's.
In some cases, it could even be argued that the ascriptive supplement has the whole clauses as its anchor, not just the NP, as it provides some explanation for the situation described in the clause.
A die-hard conservative, her father refused to even consider the
proposal.
A fan of Michael Jordan, Jack flew to the US to watch his match.