instanceof redundant for class, but not for interface

psalm is inconsistent in when it says "RedundantCondition" on instanceof checks.

https://psalm.dev/r/377cb86ce7

interface I {}
class C {}

/**
 * @param I $o
 */
function fI(I $o): void {
    // Not redundant?
    if ($o instanceof I) {
        print 'yes';
    }
}

/**
 * @param C $o
 */
function fC(C $o): void {
    // ERROR: RedundantCondition - 20:9 - Type C for $o is always C
    if ($o instanceof C) {
        print 'yes';
    }
}