Looking at this from the manual:

"The implicit form does not use the join keyword. Instead, the associations are "dereferenced" using dot-notation. implicit joins can appear in any of the HQL clauses. implicit join result in inner joins in the resulting SQL statement."

So is:

select p, p.department
from Person p
left outer join p.department

implicit or explicit?

"The implicit form does not use the join keyword" - well, this uses the join keyword ...
"Instead, the associations are dereferenced using dot-notation" - well, this also does use dot-notation

I would interpret the quoted paragraph to mean that the implicit form of a query does not use join and instead uses dot-notation. So if join exists it should be favored over an implied inner join.