LapSap, not sure of your point nor reason for the headbutt?
(1) The Jepp chart I use (10-2J 9 Oct 09 eff 22 Oct, and admittedly is tailored for my airline) does not anywhere "clearly state SPEED CONTROL Aircraft shall fly at 280 KIAS by SIERA". What it does say is "SLP SIERA" and "280 kt". That can be intrepreted as meaning either 280 at SIERA or a limit speed of 280 at SIERA.
(2) When in doubt, ask. So: ATC, when asked what it meant, replied 280 was a MAXIMUM. And they ok'd 250 over SIERA.
(3) The European carrier ahead of us obviously was even slower than 250 past SIERA, hence us being given extra track miles. No big drama. Would have still been a problem if we'd been been at 280 behind him at SIERA (us 280, him slowing to 250, indeed probably less from the sound of it). But again, no drama, that's aviation. The 5C (or vectors) is there for that sort of thing.
(4) Unless you are flying the Space Shuttle, crossing SIERA at FL190 and then being cut in for 50 odd track miles, beng at 280 kts at SIERA doesn't cut it. Well, not on the 744. It's nonsense. If you are going to be held high, you need to slow down, then convert height to speed while getting down. Flying 101. If ATC want nice, tight short arrivals early in the morning onto 07L/R, then 280 will have to be a max, not an "at" speed. Or we will just have to require extra track miles inside HKG airspace. Anyway, as I said , ATC had no problem, we didn't, nobody else did, only you seem to.
Anyway, just relaying my piece of info/experience for the greater common knowledge. Take it anyway you like.