Post the letter, or burn it!

From online blog by N. Charlow:

"The most popular way of resolving the Ross Paradox --

Post the letter!

entails

Post or burn the letter!--

is to point out that the command

Post or burn the letter!

carries free-choice permissions (i.e., to burn the letter) that are not necessarily conveyed by the command to post the letter.

Here we have a problem that looks structurally similar to the Ross Paradox (failure of imperative entailment in a case where the indicative complements of the imperative premises entail the indicative complement of the imperative conclusion), but with a vexing twist:

it doesn’t look like the failure of entailment here can be explained by appeal to permissions, for two reasons.

There just don’t seem to be any hidden permissions (certainly no free-choice permissions) in the conclusion to appeal to.

If there were such an explanation, it would seem like it could be used to block the good imperative argument.

More generally, what relevant difference between the two arguments could explain the asymmetry? I can’t for the life of me think of one."