Yeah, its possible you have a polyp that behaves normally. What is a bit surprising they apparently can't tell for sure. Do they think that maybe it's a blighted ovum? (I assume you took a pregnancy test somewhere along the way?) "May represent a polyp" is kind of a wishy-washy diagnosis, and wanting to be certain might be why your doctor is suggesting a surgical approach.
Have your periods been irregular for a while? Have you been monitored with some hormone tests? Rather than go immediately in a surgical direction, if you haven't already gotten your hormones tested, you might ask if the doctor thinks putting you on progesterone for a while and then stopping it, will give you a period that will clear the lining out. It wouldn't be invasive like a surgery, and would clear the interior of your uterus for better imaging of the assumed polyp.
I could see going with a D&C for this, but don't see the need for an ablation unless your periods have been horrible, irregular and heavy for at least a year, and ESPECIALLY don't get an ablation unless you never intend to or want to get pregnant after this. Women who have ablations and then get pregnant can actually jeopardize their lives, as the embryo can burrow into the uterine wall if it doesn't have an endometrial lining to nest in. Please decide carefully about the ablation suggestion.
In your shoes, I'd first consider whether the item in the uterus could be something like a pregnancy, probably failed but check to be sure that it's not a current pregnancy (take a home test, it will be accurate at this stage). If that's a no, ask the doctor to order some lab work of your hormone levels, maybe several times in your menstrual month, to see if your progesterone isn't stopping when it naturally would stop. That can cause the lining to keep growing. (If it's a polyp for sure, it is very common for them to interfere with the changes in hormone balance that cause periods.) I'd then okay a D&C. But I sure wouldn't do an ablation in the same operation. Only do one with careful consideration of the pros and cons. So many women have written here who regret their ablations.
Good luck!