I did wonder something similar, e.g. perhaps "greg" and "rowland" were added as synonyms for other words, or perhaps a word was completely replaced by "greg". I ruled out the synonym idea, as there is only one word with a word number of 0xC2 (i.e. greg) and one with a word number of 0xC3 (i.e. rowland).
Regarding the replacement idea, there is no "duck" or similar word in the original King's Quest WORDS list, so perhaps one of Greg's names did replace that word. The AGIv2 versions of the game do support "duck", but these early booter versions don't appear to have "duck" or "squat". There is, of course, the "-" key that makes Graham duck/squat, and that works similar to what typing "greg" does for the CGA and TANDY versions, except that for the CGA versions, "greg" squats then immediately stands, whereas for the "-" key, he stays down. For the other action words, i.e. "swim" and "jump", which have associated keys ("=" and "0"), the early booter versions of KQ do support those words, and they do the same as what the action key does... (well, it seems that the PCJR version doesn't jump when you type "jump", but the CGA versions do), whereas "duck" is mysteriously absent from the words, which is quite strange when the other two words are supported. So you could very well be on to something there. Maybe he did unintentionally overwrite a word that was doing something else.
But given that the "duck" word wasn't in the PCJR version, or the IBM PC CGA version released a few weeks after that, and yet the bit of code that supports the "greg" word making Graham crouch was added in between those two versions, I'd like to think that someone would have noticed when adding that new bit of code that it doesn't work for the originally intended word, assuming that it was added for ducking rather than as an easter egg. Maybe these releases of the game weren't properly synced up with regards to the WORDS list and the compiled scripts. If this is the case though, then all of these booter versions had the same problem. Surely they would have rebuilt the whole game each time it was released, unless the process of compiling the scripts was quite different in these early versions.