I had a similar thought and apparently it varies by the force and the country. Generally in most armies the quartermaster manages the supplies, but in the US Navy the quartermaster is the ships navigator. https://en.wikipedia.org/wiki/Quartermaster
-I feel that they should have at least tried to have a ship statblock with cannons. When most people think of ships in combat on the sea they usually think of it with cannons. Historically Cannons first appeared in the 13th century around the same time that Plate Armour was invented, cannons on ships were used as early as the 14th century. Both of those centuries are within what's generally considered the medieval era.
-If they're mentioning most ships don't have int, wis or cha they should at least have an example of a "living" ship that has those stats then. And if it could cover an enchanted Elven ship made from a living tree (thinking back to Divinity Original Sin II), could a massive Sea Turtle with big sealed howdah count as a living ship.
-There should be examples on how ship weapons target people. I assume that people on ships can't be targeted at all by ship weapons. But what about people on the coast. I feel in those cases it should be a reflex save vs. 8 + to hit. And only 1 reflex save per round, regardless of how many weapons (beyond the first one) target that person. But then it goes to what about bigger creatures vs ships.
-One round of combat on a ship still seems to be 6 seconds. Maybe in the case of ships, 1 round=1 minute like they proposed in the mass combat rules.
-I think potentially 6 attack rolls per combat round is too many rolls. I'd limit it to 3 or 4 at the most, since I like to think about cannons on ships, I feel that various weapons on ships should be grouped together as batteries of weapons. None of those weapons have a rate of fire (which they should) but batteries of weapons could be used for changing the rate of fire. Second there should be rules of which direction weapons can fire in relation to the ship.
-At least a few more examples of exotic ships, like maybe one of a ship with Elemental Bombards and Arcane Lances, or a Merfolk boarding submarine or something like that.
Between this, the Ship mini coming early next year, and the D&D comic set in Mintarn coming in February I definitely think the Spring book (that Kate Welch was the lead designer on) is a High Seas book of some kind. I do not believe it is an adventure book (because they have gone away from doing two separate Adventure paths in a year unless they are connected like DH and DotMM).
What I think we get is a second Tales from the Yawning Portal but for High Seas adventures. Something like "Tales from the Sea of Swords" that has a chapter on High Seas ships and rules, then a bunch of smaller Adventures for folks to use with the rules. No big story or anything, just a supplement to enhance adventures to give folks some High Seas feels.
or maybe is a random choice and we try to find a sense on it.
I don't consider them as rational as they seem to be, neither I don't think they have a really detailed plan for the future, but you know, it's just only me as usual