Jones the Alligator achievement possible bug?

[Punished "Venom" Bateman]

I decided to play Hotline 1 again, and I went into to the sewer on level 5 (IIRC) to see the Jones easter egg. I'd already done the easter egg and I even completed level 5 with the Jones mask equipped, but just now I got the achievement. Is this normal?

[Mandrake]

Yes, it's a known long-standing bug that affects everyone