Well, I was browsing the SMS Power forums earlier today when I saw somebody mentioning this:
Both Sega Power #25 (cover date December 1991) on p11 and Sega Pro #1 (cover date November 1991) on p9 list "DuckTales" on SMS as due November 1991. Then in Sega Pro #2 (cover date December 1991) on p7 it says "Donald Duck" on SMS is due December 1991. Then in Sega Pro #3 (cover date Christmas 1991) p24 it says "Donald Duck" on SMS is due "before Christmas ". Then in Sega Pro #4 (cover date February 1992) on p30/31 they review "Donald Duck The Lucky Dime Caper" on SMS and say it's out now. Pretty clear evidence in these consecutive issues of it being the same game simply evolving. Plus several other gaming magazines review the Lucky Dime Caper around this time as well (many are listed on the SegaRetro page in the reviews box)
In my view it's very unlikely there would be two Disney games on SMS due for release so close together, plus The Lucky Dime Caper includes several DuckTales characters in the story/intro so it's not much of a leap at all. In my view this is more than enough evidence to show DuckTales on SMS is just the original title for The Lucky Dime Caper and it was never a separate game.
What about Quackshot? Well, I'd say that this does make a bit more sense when you look at it with the possibility in mind:
Duck Tales movie (1990)
There's even a couple of details from the in-game logo that are based directly on Duck Tales' and don't appear in the box art, like the overlapping "K" and the distinct shape of the "T".
Then, there's the very possible reason why Donald is not wearing his usual overalls:
...But this is as far as facts get without entering speculation. Unless somebody has already found any further evidence?