I thought so too, but sorcs don't get that bonus. After JC noted this in a thread about Kelsey's Int, I tested it myself by making new sorcs with 10 Int and 18 Int. No difference in number of spells between them.
I just had a closer look and it's probably not a bullshit at all. INT does not give you any bonuses but if you have INT lower than 19 you get limits to maximum spell level and spell slots per level. So int can affect sorcerors in the same way (as the manual claims)
Fine, let's try this again. This morning I uninstalled any EXP/class/level affecting aspects of Ease-of-Use, then started two new sorcerers, alike in all ways except for Intelligence. Sorcerer A had 18 Int, sorcerer B had 9 Int. Both started at 7th level, then I leveled both up to 20th by adding 40 million XP. For high-level abilities, I picked new spells rather than extra spells per level, these are noted in the level 9 scribed spells as the "bonus" spells.
Sorcerer A (18 Int) started with the following spells:
1st - 6 castable, 5 scribed
2nd - 6 castable, 3 scribed
3rd - 4 castable, 2 scribed
At level 20, she looked like this:
1st - 6 castable, 5 scribed
2nd - 6 castable, 5 scribed
3rd - 6 castable, 4 scribed
4th - 6 castable, 4 scribed
5th - 6 castable, 4 scribed
6th - 6 castable, 3 scribed
7th - 6 castable, 3 scribed
8th - 6 castable, 3 scribed
9th - 6 castable, 3 scribed (+ 3 bonus)
Sorcerer B (9 Int) started with the following spells:
1st - 6 castable, 5 scribed
2nd - 6 castable, 3 scribed
3rd - 4 castable, 2 scribed
At level 20, she looked like this:
1st - 6 castable, 5 scribed
2nd - 6 castable, 5 scribed
3rd - 6 castable, 4 scribed
4th - 6 castable, 4 scribed
5th - 6 castable, 4 scribed
6th - 6 castable, 3 scribed
7th - 6 castable, 3 scribed
8th - 6 castable, 3 scribed
9th - 6 castable, 3 scribed (+ 3 bonus)
Those are exactly the same. Same number "scribed", same castable per day, even the same high-level spell abilities. Int doesn't do jack for a sorcerer. (Outside of any game-related incidents that require a high Int, like being able to access certain conversational options, but that's true for any PC regardless of class.)