I mostly agree with two and a half exceptions in AD&D where the benefits of stats were insane. One is a corner case and doesn't affect combat much- Dexterity for Thieves. The benefits for the higher Dex scores could equal having a free level (or more). An argument could be made for the increase to AC as well, but it was unlikely a heavy armor user would also have really high Dexterity (though if they did, it's entirely possible to build a starting character in 2e with an AC of 0).*
And of course, exceptional Strength for the Warrior classes. The scaling got out of control quickly.
Most characters didn't get ability scores this high, but if they did, it really warped things around them- the difference between a Fighter with 17 Strength and one with 18/50 was definitely noticeable, and if someone actually got to the 18/90-00 range, it was like being multiple levels higher, and many early monsters died in a single attack (of which the Fighter could have as much as 5/2 with Two-Weapon Fighting).
Constitution being the last, though again, for Warriors. An extra 9-18 hit points doesn't sound incredible by today's standards, but you could be looking at a 33% increase to your hit points by level 9 (assuming dead average rolls and maximum hit points at level 1).
*18 Dex, Warrior with Swashbuckler Kit, leather armor, and 2 weapon proficiency slots in Single Weapon Style from the Complete Fighter's Handbook.