A bonus action is not an action, though. You can't just convert one to the other. The bonus action rules explicitly say that you get to decide when you take your bonus action (if you have one), unless the bonus action itself specifies a timing restriction or trigger. JEC has clarified this on Twitter, in response to questions along the lines of the discussion we're having now:
https://www.sageadvice.eu/2018/05/23/clarification-about-bonus-actions/
In particular, the section with the following:
"It’s not just about shield master or triggered bonus actions when you say that no rule permits a bonus action between multiple attacks."
...
"But you wanted to know where you said no bonus actions between attacks. I identified the phrase. Whether you meant that or not, that’s what you said here."
"Ah ha! Now I get what you're driving at. I was focused on bonus actions with triggers. You're talking about bonus actions without triggers. I'll clarify things! Thanks for your patience."
The in the Sage Advice video also talks about how actions and bonus actions are separate things.