Ancestry's hints and the suggested parents feature both work the same way.
Ancestry compares the people in your tree with the people in other trees, looking for similarities. When it sees someone else with the same name, born in the same or similar location, with spouse and or children with the same names, it guesses that they might be the same person, and hence suggests hints based on that guess.
In other words, all it is doing is suggesting a person or document that someone else added to a person in their tree, that Ancestry thinks might be the same person that you have in your tree.
As long as that other person is in fact the same person as is in your tree, and not just a similar namesake, and as long as the information the owner of that tree has added is accurate, everything works fine - but if the two are not in fact the same, or the other person has added a relative or a document in error, the associated hint will be wrong.
Ancestry's hint system can be highly useful - it can also be highly misleading. The simple rule is to always check the documentary evidence yourself. Never just accept Ancestry hints without first checking any relevant documents. If a hint came from someone else's tree, take a look at that tree to see if it does seem to match the information you already know.