I don't think it's all that unusual. These boats are 35 years old. Several examples of boats I looked at had similar looking cracks. Only a problem if the crack goes all the way to the wood core.
Again, it might help to go look at other boats. Any time you're working with a field of "one," it's hard to discern what is unusual versus what it common for 35 year old boats.
Again, it might help to go look at other boats. Any time you're working with a field of "one," it's hard to discern what is unusual versus what it common for 35 year old boats.