I believe many, many, many moons ago, this was the case, at least on an ad-hoc, not-in-the-rules basis (i.e. it depended on the front desk agent, because the entry cards were always - and still are - rather flaky).
In November 2012, my QF F arrival, linking to a BA J onward flight to CDG, gave me entry to the LHR Concorde Room, with not a hint of hesitation from the sentry point outside or the reception point inside.
Did receive a snippy refusal from the Spa desk, as my onward flight was not long haul F. (Their explanation - which is too polite a word for the exchange.)
Was not really bothered. Had a long layover and thought it could pass the time pleasantly but had more than enough to do and bubbly to drink.
On balance, I prefer the T5 F Lounge but it was interesting to check out the CR.