Would you feel it's a bad sign getting hired and start working the same day as your job interview?

My boyfriend had a job interview this morning and just over an hour after his interview, he got a call saying he got the position and that he could start working this afternoon. He accepted and was pretty happy, but as we were talking more about it, he started feeling a bit iffy. He says he's never started working so quickly after a job interview and was worried it might be a red flag. But he'll be working at the same complex my mom works at as a groundskeeper and she reassured him that they're always looking for more groundskeepers where she works and tend to fill those spots as quickly as they can; that it's not bad work and the management is decent.

I myself have been hired the same day as a job interview on more than one occasion. I didn't start working the same day, but I was still hired pretty fast. I never saw it as a bad sign.