Wrestlers are humans. Humans can fight standing up. Boxers are humans. Humans can fight on the ground. Skills do not guarantee success, or even clear advantage.
In theory, I'd agree. In practice, however, I cannot. To keep with boxers and wrestlers....
I've never seen a boxer instictively or intuitively perform anything that resembles a correct escape from the ground to return to their feet without being trained to so. Could it happen? Maybe. But I'd say the odds are pretty much the same as an untrained person performing a technically correct sankyo on an uncooperative nidan.
Certainly a wrestler can punch (or kick, or elbow or headbutt) without being trained to do so. But such strikes are hardly threatening to a skilled striker. The form, technique, timing, accuracy, placement and setups are terrible. This is why boxers train so very hard to get good at punching, it's not an easy thing to hit an uncooperative opponent effectively.
Simply put, we will never see an NCAA Div. 1 wrestler just walk into the ring and win the Golden Gloves without training in boxing. Nor will we see a boxer set onto the mat and equal Cael Sanderson's feat of an undefeated collegiate wrestling career without thousands of hours wrestling. Both groups lack the skill set of the other, and cannot compete in different environment.
A world class marathon runner isn't going to win a swimming event at even the collegiate level...running is not swimming and the skill set simply isn't there. I don't think anyone would expect the runner to fare well in a swim meet...why would martial skill sets be different?