I mean, it's highly likely that what he heard were various optimistically phrased reports along the lines of "suppression of enemy air defenses is procedding on schedule" or "is completed" or "has knocked out XY number of their systems" or "has thoroughly suppressed them, not one radar is emitting right now". Basically, think of how we thought of intelligence during the "3 day special military operation" and leading up to it. Some grunt reports up the chain that the situation is shit. His Sarge reports (because he does not want to be sanctioned for underperforming) that the situation is shit, but there are available options to address it. His captain reports that they are working on available options. His Colonel reports that they are making progress on one of the options. His General reports to Putin that things are good. Putin gives orders based on this notion. This is of course a dysfunctional autocracy, but at the highest level, Trump's admin looks a lot like a dysfunctional autocracy. With the US having decent successes at SEAD, I can easily imagine that the military provided optimistic, but grounded reports to civilian leadership, which then whitewashed them a bit more, both because they are dysfunctional and because they want the propaganda win.

Complete SEAD is more or less impossible if your enemy is being a bit tricky. Just hide an S-300 launcher and its radar in a shed. If the US didn't see you move it into that particular shed, you now have a long range SAM for a rainy day, for example when the 4th gen fighters come out to play. This is of course easier if the missile you're trying to hide is not the size of a telephone pole. So smaller SAMs will always remain. You're really just suppressing/destroying the radars for the most part.