In a non-searchable and potentially ephemeral comment to the original posting, Professor Lawler kindly presented the following answer:
The inherent ability sense is alethic, not deontic.
The deontic usages are about permission, and epistemic ones about logical possibility. Epistemic can is a negative polarity item:
- *This can be the place.
[Where the asterisk denotes an ungrammatical form. ―tchrist]
In the right context, that clause could be any of the three. As a standalone utterance, shorn of context, it’s ambiguous between deontic (he has/had the necessary permission) or alethic (he has/had the necessary ability). Not epistemic, because there’s no negative trigger in this sentence (the than clause of comparatives is negative, but not the compared clause).
See umich.edu/~jlawler/Modality.pdf for more on English modality.
I’ve marked this posting Community Wiki because it is John’s answer not my own, and so I deserve no reputation from it.