Does "small hints" sound odd to you? Google Ngram shows that almost none uses it while a majority of people use "little hints" or "few hints": Google Ngram.
There could be several stars made of antimatter in our solar system’s neighbourhood. There have been small hints that these strange and unlikely objects, called antistars, could exist, and a search for the gamma rays that they are expected to produce has turned up 14 candidates.
Source: New Scientist
Just as there is a difference between "small birds" and "few birds", there is a difference in meaning between "small hints" and "few hints".
Small hints are hard to notice. They are subtle: for example a graph could have a very small bump on it that should not be there, unless "antistars" exist. The hint is small. It is quite common to speak of "a big hint". It is less common to talk of "a small hint"
On the other hand "few hints" means "a small number of them". They could be very big hints... but there are not many.
I'm not disputing @James-K's answer, but I'd add to it in the following way:
I think the main reason that 'small hints' is not much used is because it is a tautology. Hints are by their nature expected to be 'small' and 'little'. A 'big' hint needs to be described, as it departs from the expected insubstantial nature of a hint.
So, the two examples below mean exactly the same thing, and if I were proofreading the text, I would cross out 'small' as unnecessary. 'Big hints', by contrast, would mean something very different, and 'big' would be adding substantial additional meaning to the sentence.
There have been small hints that these strange and unlikely objects ...
There have been hints that these strange and unlikely objects ...
