In fact, we see Shanks in Chapter 0 looking much younger than a 24 year old looking for a crew of his own, and also based on the pages Oda designed for the Red movie, Shanks had no scars on his face when he formed his crew. Oda literally destroyed the timeline. Shanks lived with Garling for nearly 7 years, and we thought he only went to MG for a short visit. The discrepancy is greater than I thought.
Unless Shanks was secretly looking for a crew for himself, which doesn't make sense.