Almost certainly yes. And this is not a reproach aimed at agencies: it is a structural feature of how self-assessment works, and it is measurable.
What we measured
In IKAg's COLLAB benchmark there are nine cases where an agency was rated in the same round both by itself and by its client. In nine of those nine the agency scored itself higher than its client did. On average 1.4 points out of ten higher, with outliers of 2.7 and 2.4 points.
Nine is a small number, and it is honest to say so. But nine out of nine in the same direction is not chance, and it matches what comes out in the conversations themselves.
Why it happens
An agency sees the effort, you see the result. They know how much work went into that proposal and what was polished afterwards; you see the proposal.
Bad news does not travel upwards. The account manager who knows you are unhappy is not necessarily the person telling their management. So internally it gets reported that things are fine.
You do not say it. Most dissatisfaction is never voiced to the agency, and then it is reasonable for them to think it is going well.
Why it costs you
An agency that thinks things are fine changes nothing. It does not put more seniority on your account, it does not revise its approach, and it is genuinely surprised when you launch a pitch. That surprise is usually real, and it is the most painful part.
The intervention that fixes this
Have both sides answer the same questions, in the same period, anonymously, and put the two results side by side. The conversation then is not about whether things are going well, but about why you see it differently. That is a conversation that moves forward, because there is data on the table instead of a feeling.
Do it annually, so you build a series. See how to evaluate your agency and what a normal satisfaction score is.
See also: why the collaboration is grinding.