That is overthinking it. It's simpler just to assume they were saying "phasers" in "The Cage" all along, which is no doubt what Roddenberry would've preferred (just as he preferred to believe that Klingons always had ridged foreheads). He changed it because he decided calling the weapons "lasers" had been a mistake.
After all, going by that Czech closed-captioning transcript site
, the word "laser" is only used twice in the whole pilot. Easy enough to gloss over. Also, there's no way a laser could build up a "force chamber explosion" -- that's not how a laser works.