If a key has more than one UID and one of them is not certified, it is shown as "not certified" in the certificate list.
But when you select such a key in the sign/encrypt dialog, a green check is shown next to it. Although it says "not certified" behind the key-id, the thing one's focus is on is the green symbol, which is misleading.
For non-vsde-enabled installations the green check symbol is okay because in the given context (encryption) it indicates that the key can be used.
On the other hand, in vsde-enabled installations the key cannot be used for compliant operations. Therefore, in this case using a different symbol may be better, so that the user can immediately spot the problematic certificate.