When a mixed blend makes sense
Use a mix when one part of the yard is sunny and exposed while another part is broken up by tree or structure shade. A blended approach can smooth out a lawn that does not behave like one single zone.
When it becomes a marketing shortcut
If the entire yard is full sun, you may be better served by choosing a grass family directly instead of relying on a catch-all bag name. The same is true for deep-shade problem areas.
What to compare next
Most buyers should compare this idea against the shade guide and the main best-seed page before purchasing.