Incidentally it’s AN 3.63 on SC.
This issue was discussed on DW a while back - http://www.dhammawheel.com/viewtopic.php?f=43&t=18276&hilit=aorist
The member called pulga helpfully called attention to the possibility that the Commentarial and Bhikkhu Bodhi explanation may have been prompted by the understanding that the phrase “evaṃbhūto caṅkamāmi” is a periphrastic construction that gives “while I walk in that state”. This on the basis of Warder’s listing of “tuṇhībhūto nisinno hoti” as a double-periphrastic (p.239).
Yet, I find that Warder is somewhat restrained, and gives only the double-periphrastic example involving tuṇhībhūto and nisinno as the 2 governing verbs (as past participles) with hoti as the auxillary verb. I’ve looked in the texts at nisīdati (the present indicative) and could not find any examples of nisīdati participating as an auxillary verb in a periphrastic construction.
This leads me to conclude that “evaṃbhūto caṅkamāmi” is not a periphrasis. In fact, I am not sure if conditional statements such as the AN 3.63 passage can ever be periphrastic (the passage uses ce/if).
If we disregard the Comy gloss on this passage, I think we can also translate the passage legitimately as such -
So ce ahaṃ, brāhmaṇa, evaṃbhūto caṅkamāmi, dibbo me eso tasmiṃ samaye caṅkamo hoti.
Having become thus, if I pace, , on that occasion my pacing is celestial.
What I have done is follow the CPD in treating evaṃbhūto as an adjective qualifying the Buddha, rather than as an adverb qualifying the action of walking.
Then, the problem goes away.