That made me think that this strory is true. Otherwise, McLaren would have been very quick to deny this as they had done a few days ago with a quicker-than-quick denial about speculation on PURE engines. The way McLaren and Autosport handled this incident creates more confusion and covering up. That's the last thing you may want to do in a heavily digitilized and connected world. That is poor PR.
On the PURE issue, McLaren were denying "rumours", not direct quotes from their own staff. The McLaren denial may even have been a response to a question from a journalist rather than an unprompted press release. As for "quicker-than-quick", the Autosport article says
The Woking-based team has been the subject of rumours for months that it could opt to change engine partners when Formula 1 switches to V6-turbo power-units from 2014.
Although the team said last November that it was fully focused on ensuring future success with Mercedes-Benz, amid rumours linking it with Honda at the time, that has not stopped a number of reports in recent days suggesting that Pure is now being considered.
Autosport's pulled article, on the other hand, had direct quotes from a McLaren member of staff (a senior one, at that). If the article is true, or at least the quotes are genuine, then Autosport are on firm ground and have little to worry about by publishing. If the article is untrue, or the quotes are fake, then Autosport are on very dodgy ground, and simply publishing a correction may be inadequate.
I can think of several possibilities:
1. The article was materially false, either by accident or design.
2. The article was written using embargoed material and was published too early.
3. The article used quotes and/or an interview that hadn't been authorised or supervised by McLaren's PR and pressure was applied by them to have it removed.
4. McLaren realised with hindsight that the article did not make good PR and they pressured Autosport into removing it.
To me, the fourth option is the least likely, and the third is not a lot better.
Too many people know about the article, despite the brevity of it's existence, for Autosport to pretend it never happened. I think they would be wise to publish some form of explanation. Secrecy and journalism make unhappy bedfellows.