This might help:
body {
-epub-hyphens: none;
adobe-hyphenate: none;
-webkit-hyphens: none;
-moz-hyphens: none;
hyphens: none;
}
The above css turns off hyphens for: ePub3, ADE, Safari & Chrome, and Mozilla/Firefox, generic, respectively.
As I understand it, {adobe-text-layout: optimizeSpeed;} forces the reader to revert to an older version of ADE (RMSDK 9.1 rather than 9.2) that doesn't have hyphenation functionality. That's why it gets rid of hyphens. But you also lose whatever other improvements 9.2 has over 9.1.
I don't have a T3 to test this on, but I'd be curious to know if the above works. If anyone tries it, please post results!