For polymorphic functions it looks like only the first signature is picked and shown when typing.
In the example below v is of a numeric type, but the tooltip is showing only the signature with a date field as first argument.

Also, bucket could accept up to 4 arguments: why showing a signature only a signature with 2 args?

It would be a better experience to filter out incompatible signatures with the current function arguments.

This feature is a complementary part of autocomplete: the suggestion system relies on the user that has to "remember" the function signature while typing. If a wrong signature is shown, this undermines the value of the autocomplete system.
As a user I can see how the suggested values are potential good candidates for the argument in that position, but if I cannot see what's the context of the argument in the function signature or see mismatch between the signature and the offered values the autocomplete becomes less and less valuable.