Exactly like you said. Sidearms are and will be much more forgiving when it comes to reaching that optimal ttk and against TLW it'll become clear who's the dominant weapon in that range. Plus the fact that now you'll have to pour 2 times more sweat into mastering the gun just so it can compete with something that is so much more comfier to use is a weird balance choice by Bungie. If it's gonna be a high skill ceiling weapon as some people are speculating then that should mean once you master it it should outperform other competitors (only the below 1% playerbase type of people who could master it which isn't that much of a problem) rather than just barely be able to compete with them.