Instinctively, I've often felt it might, but I wonder if that's how other people think.
Some context: I have worked in TV for a long time. I tried to become an editor, it was basically my dream to be a film or TV editor. This career didn't really work out. I had one or two credits to my name, but I couldn't convince my local industry to take me seriously and I never made that short list of people here who are regularly called to do this and no one really thinks of me as an editor. I ended up pigeonholed in to a technical role which I've spent most of my career since doing in order to make a living. It has been very depressing and disheartening to watch the dream wither.
Recently there was a bit of a seachange for me. I was unexpectedly plucked from my rut and put in to a colour grading role. I knew a bit about grading and had always liked it but was definitely not at that point someone I personally would have picked because of the lack of any credits in the role, and the lack of expert level proficiency normally required to do that for Television where speed, efficiency and accuracy are very important. As it happened, I loved it and I was able to rise to the occasion just fine and it's led to other credits since. I think I might finally have the career path that I actually like and feel some self-respect having.
However, the thing is I never truly gave up on being an editor, I just didn't really succeed as I'd like to have done and have begun following this colourist path basically because it just opened up in front of me. I recently completed colour for a series and it's been commissioned for a second series. I did well at that company and both myself and my work were well received. While there I vaguely raised the subject that I also edit and would love to do that for them if they needed it. I know for the second series they're likely to call me in for colour once more, and I know that they are doubling the number of episodes this time which would mean they will need more editors than last time around so while they'll definitely call in the old crew, maybe there's a chance they might be happy for me to do that as well as the colour. The thing is, if they don't themselves think of this and ask me about it, I wonder if mentioning it myself explicitly might backfire on me. I worry that if they turn out not to be interested in having me edit, the very act of mentioning it that second time, might lower their estimation of me as a colourist. I'm worried it might give off some air of arrogance, or possibly desperation, and maybe it'll look like I didn't really want to be a colourist or I'm not really interested in it which might sour them on hiring me for that role too.
Is this a valid concern? Is it poor form to try and snag additional roles when a company knows you for another? Would it make me look like a jack of all trades and master of none?
I get the feeling you're like me and you might be over-thinking it. If you're new, if I heard it, I'd pass it off as you sharing your skillset. Remember they hired YOU because they believe you can do the work.
If you want to help them edit, ask to sit in on their sessions. Tell them you want want to be a fly on the wall to see the process, etc. I've done that in the IT world with great success. It shows you're curious and eager to learn.
If they say no, then you have your answer -- they may be only looking to you to fill one box. Most managers understand that you want to do more than what you're doing now.