If "check" means "dice roll", then why? It's mighty anachronistic to expect the old game to advocate principles of the new. All the DM needs to give is what the characters perceive.
A fighter cannot do all that the thief can in regards, say, to creaking floorboards or squeaking hinges. Nor can the fighter so blend into dark areas, flatten himself or herself, and, by remaining motionless when in sight, go unobserved.
It is hardly necessary to turn everyone (including thieves with mere 10% or 15% chances in their special functions) into clumsy bumblers! That is most definitely a "house rule", for which those contriving it are responsible.
You seem to have ignored the second half of the sentence of mine that you quoted, which seems to me like it should have been relevant to your response. In case you are uncertain, I'm referring to the following:
...or that you should role play the encounter entirely without dice.
The system of AD&D/OD&D pretty much assumes that (low level) PCs are clumsy bumblers at a great many things by default!
Again, I'll ask you to demonstrate where in the AD&D PHB or DMG it was suggested that the players should be able to overcome challenges via free form role playing.
Because I would say that "An Example of Play" on page 10 of the 2nd edition PHB seems to run somewhat counter to what you are saying here. The DM rolled several checks for the players to locate the secret door, which barring the presence of an elf could have easily been failed. The example explicitly
didn't have the PCs automatically succeed in locating the secret door when the cleric stepped onto the block and searched the ceiling; stepping onto the block merely gave him the opportunity for a 1 in 6 chance (I think that was the non-elven chance anyway) to find it. Not very good odds, though I suppose it didn't matter for whoever wrote the example as I doubt they actually played through the scenario.
It isn't as obvious as you seem to imply (as my play experiences can attest to). If it wasn't present in the books, then you are house ruling. Don't be mistaken, I think that allowing your PCs to cleverly circumvent a 90% chance of failure is an example of good (or even great) DMing, but I'm 99% certain that it would also be a house rule under AD&D.
Free form RP is something that you can do with any game (or even without a game), be it 4e or AD&D. 4e just provides a robust and balanced mechanical system in addition to whatever free form RP, because when the DM is too inexperienced or simply uncertain whether a plan of action ought to succeed it's nice to be able to fall back onto something actually functional.
