A couple of things that strike me:
1. They are called "Ability" scores instead of attribute scores, stats, etc. The word "ability" is also used throughout the descriptions.
"Strength" is a measure of muscle power and the ability to use that power.
"Intelligence" is the ability to learn and remember knowledge, and the ability to solve problems.
2. I noticed a number of times in the descriptions terms (or closely related terms) that become "skills" in later editions - balance, endurance, intuition, knowledge, etc.
Ability scores are more than just the raw characteristics of a character. They also reflect the ability to harness these characteristics into actual abilities. You don't need a swim skill to know if the character can swim across a raging river. A DM can reasonably determine if a character can swim based on his background. He can take a look at the character's strength and see of he has the ability to harness his strength to swim across the raging river or he can ask for a save vs strength or any other mechanic to let the dice decide.
Ability Scores + Class give all of the skills anyone could possibly use.