Those calculations are unbuffed and recipes are not noted at all which should be since they are part of the complete picture regardless of the level limit when it comes to the game design. Bookbinder and rarity max buffed for one day is around 15 manuscripts which for example means all 46 generals would have a maxed jog in about 10 days. There are plenty of ways to get bookbinder and provision house buffs.
Remember that their (BB) business is to also sell some gems which some people use to buy glue or quick complete books.
Anyways the chart example is also a bit unrealistic since there is no need to max skill that many and especially in a such linear way so lets halve the amount and time to, say 4 years. Then include the recipes which unbuffed roughly halve the time again to 2 years. Finally count some buffs, glue for 2x and rarity up to 4x division with barazeks. That gets us roughly to 1 year or less if we assume we buff "often". On top of that include all the event calendar books and other possible random sources. It does not take that long after all when BB does the math based on dedicated players (such as the player with 46 gens).