That’s true, but a generally accepted fact of life employers have to cope with. They don’t have to cope with employees taking on another responsibility next to their existing job and family.
As long as it doesn’t interfere with you performing your contractual duties to your employer? Sure. Although that can include showing up to work tired because you spent your night tending a bar, using knowledge acquired at your primary job for your side gig, or being unfocused in meetings because you constantly think about the other venture.
So instead, you might just want to check with your employer beforehand and talk about what they’re cool with. Something Sams could have chosen to do, but did not, apparently.