As explained by All Might in the main series, people may not know the actual scope of their powers or how they really work. Hence why people are allowed to change their quirk in the registry once or twice without any issue. Koichi is a perfect example of how something like this could occur. His quirk is considered 'slide' because he only ever remembers using it to slide since his mother would always smack him with her quirk when he was a baby to keep him from flying off and hurting himself. His only memories of it that weren't staved off with memories of punishment were 'slide', a non dangerous use of his real power 'propel' and 'attach'.
Judging by Akaguro's clothing when he changes out of his 'Stendhal' outfit, he appears to perhaps be some form of handyman or janitor. This makes a bit of sense on a couple of levels. Thematically, Akaguro considers himself to be 'cleaning' up the Hero System and society through his work as a vigilante. However, more practically, we know from the main story that Akaguro became a high school dropout after becoming disillusioned by the Hero System when he was young. Since many jobs require a high school degree at bare minimum to qualify, something which he presumably does not have, he would have had to take such types of jobs in order to earn money.
Koichi also show a perfect example on why aspiring hero-students have pro-hero advisers available when it comes to baptizing their attacks and hero identities. His sense for attack-calling and hero-names are downright cringeworthy without that assistance/judgement.
