Although this one is not from the Basic rules, it does seem acutely relevant. The PHB predated Moldvay's rules by three years. My suspicion is Could it be that when the Basic rules were written this detail about the thieves' ability was already so well understood as to be assumed, so that neither Moldvay nor his proofreaders ever noticed that he failed to state it explicitly.?
- Module B3 PalacePalace of the Silver Princess (Module B3) by Tom Moldvay, Entry 53, Page 12
AlthoughNow let's not all start hyperventilating. Although Moldvay is credited as author of the module, he didwas not necessarily writenecessarily the author this inconvenientparticular passage. Module B3 had a complicated history (read the Wikipedia article). It credits several people with "Development" in addition to Moldvay and he is not listed under "Editing". Furthermore, the awkward structure and multiple grammatical errors in this passage suggest to me at least the possibility that someone other than Moldvay could have written it. And let's not overlook that the rule itself simply beggars common sense.! That venerable Moldvay wrote those words with full cognizance seems unfathomable to me. Yet there they standare, and his name on the cover. Each man must reconciledo bloody battle with the fact in the coliseum of his own thoughtsmind.
Grudging thanks to Kaique de Oliveira for bringing this rather unfortunate passage to my attention in his answer onlight this pageintriguing, if inconvenient, piece of the puzzle.