Recall that Pronto Hex simply lists the durations of the on and off flashes, with the first 4 words describing frequency and number of burst pairs.  Here the on durations are always short (e.g. 001c, 001f, 0020) while the offs have either a short or long (e.g. 003c, 003d, 003e) duration. Taking shorts as 0 and longs as 1, we have in binary
101000010101011 for learns 1 and 3
101000010101000   for 2 and 4
101000010101010   for learn 5.

I don't know why the last three bits change.