In our system it implies a major piece of work that can almost always be split down into multiple tickets that can usually be worked on in parallel.

2nd Splitting it in smaller parts forces you to examine all the parts and inner workings. Sometimes you will realise entirely different solution is needed, sometimes that there is an api call that will incur costs… and some of these things definitely have to be communicated to stakeholder, ideally before you spend significant times in development.