Brake bleeder valve

[Brendan65]

So I went to flush the brake fluid (first time with this bike) and cracked the bleeder ... but no fluid was coming through the nipple.
I figured it was probably rusted/clogged but when I removed the valve there were no holes at all - it's like a bleeder "plug".
Has anyone ever seen something like this ?
I'm ordering replacement bleeders anyway as one was quite corroded.