I voted it depends.
Blunt directness judiciously and respectfully applied, sure, especially if they’ve taken time to build a foundation in the relationship that can bear that.
Honesty, always, even if it’s just shutting up and listening because they understand that what they are actually thinking might not be helpful and might be their own stuff. But honesty can almost always be tempered with a filter of tact and compassion.
No holds barred unfiltered feedback without being tempered with tact and respect is rarely helpful in any relationship.