'Apollyon' in Rev. 9 simply means 'Destroyer.' 'Apoleia' in Mt. 7:13 means 'destruction.' I don't think the NWT has 'modified' anything, in this case.
However, it is a matter of interpretation who that Destroyer is. OK, the 'Revelation Climax' book contains a lot of hooey and some of it is even out-of-date by WTS standards, but whether the Destroyer is Satan or Jesus, it is INTERPRETATION, not WTS deception that may be at fault in this instance.
The issue raised by this thread title isn't so much the identity of Abaddon as the locusts who come out of the abyss. According to WT interpretation it is the JW's themselves who have been abyssed and released. Methinks they didn't think the whole thing through, as usual.
Besides, the picture in the Revalation book was kinda scary and made them look like some genetic mutation involving ancient babylonians, or something. Another faux pas?