It sounds like you’re describing a situation like:
A: [to B, in advance] they asked me to bring drugs into the country illegally.
C: [to B, in fact checking] yes, but the drugs were over-the-counter medications and we thought it was legal.
A: [to B, after fact checking has begun] C told me about the drug thing and asked me to retract my claim. I didn’t lie to you, but I probably should have mentioned that they were OTC and C didn’t know they were legal.
With this strategy B would ignore that A agrees with C’s clarification. And would also ignore it if instead it had been:
A: [to B, after fact checking has begun] C told me about the drug thing and asked me to retract my claim, but is thinking of a different time; I was taking about the crack.
If it’s important to A that C cannot retaliate against them to shut them up and they’ve decided to use the precommittment process I’m proposing, this requires giving up some flexibility. In this case the time for B to get clarity from A on exactly what they’re claiming would have to be before starting the adversarial fact checking process. Once it has started, all B can do is consider what they heard from A before fact checking and what they’re hearing from C now and choose between keeping the claim, weakening it, clarifying it, or dropping it.
Note that weakening it is quite tricky: you can’t do it in a way that makes it sound like A is claiming something different than they already endorsed before fact checking, so if you do want to keep the claim I think clarifying it will often make more sense. In this scenario I think I’d go with something like “A told me C asked them to bring drugs into the country illegally. During fact checking C agreed that it wouldn’t have been legal, but also said they were over-the-counter medications and at the time they made the request they believed bringing them in was legal.” And then potentially adding “Due to the precommitments to our sources I described above, I have not asked A whether they agree with C’s description of the situation, but even if C is correct I think it demonstrates a reckless attitude toward the sensitive matter of bringing controlled substances between jurisdictions.”
It sounds like you’re describing a situation like:
With this strategy B would ignore that A agrees with C’s clarification. And would also ignore it if instead it had been:
If it’s important to A that C cannot retaliate against them to shut them up and they’ve decided to use the precommittment process I’m proposing, this requires giving up some flexibility. In this case the time for B to get clarity from A on exactly what they’re claiming would have to be before starting the adversarial fact checking process. Once it has started, all B can do is consider what they heard from A before fact checking and what they’re hearing from C now and choose between keeping the claim, weakening it, clarifying it, or dropping it.
Note that weakening it is quite tricky: you can’t do it in a way that makes it sound like A is claiming something different than they already endorsed before fact checking, so if you do want to keep the claim I think clarifying it will often make more sense. In this scenario I think I’d go with something like “A told me C asked them to bring drugs into the country illegally. During fact checking C agreed that it wouldn’t have been legal, but also said they were over-the-counter medications and at the time they made the request they believed bringing them in was legal.” And then potentially adding “Due to the precommitments to our sources I described above, I have not asked A whether they agree with C’s description of the situation, but even if C is correct I think it demonstrates a reckless attitude toward the sensitive matter of bringing controlled substances between jurisdictions.”