Inconsistent spellcasting benefits from prestige classes?


Am I reading these rules right? There seem to be some strange inconsistencies in the benefits some prestige classes grant to the base spellcasting class. Here are some examples, all from the 3.5 DM’s Guide (although the inconsistencies continue in other rulebooks).

Archmage (page 178) buffs spells per day and spells known, but doesn’t mention caster level:

When a new archmage level is gained, the character gains new spells per day (and spells known, if applicable) as if he had also gained a level in whatever arcane spellcasting class in which he could cast 7th-level spells before he added the prestige class level. He does not, however, gain any other benefit a character of that class would have gained (bonus metamagic or item creation feats, and so on).

Eldritch Knight (page 188) buffs spells per day and caster level but doesn’t mention spells known:

From 2nd level on, when a new eldritch knight level is gained, the character gains new spells per day as if she had also gained a level in whatever arcane spellcasting class she belonged to before she added the prestige class. She does not, however, gain any other benefit a character of that class would have gained (bonus metamagic or item creation feats, bard or assassin abilities, and so on). This essentially means that she adds the level of eldritch knight to the level of whatever other arcane spellcasting class the character has, then determines spells per day and caster level accordingly.

Loremaster (page 191) buffs all 3: spells per day, known, and caster level:

A loremaster continues training in magic as well as her field of research. Thus, when a new loremaster level is gained, the character gains new spells per day (and spells known, if applicable) as if she had also gained a level in a spellcasting class she belonged to before she added the prestige class. She does not, however, gain any other benefit a character of that class would have gained (improved chance of controlling or rebuking undead, metamagic or item creation feats, and so on). This essentially means that she adds the level of loremaster to the level of some other spellcasting class the character has, then determines spells per day, spells known, and caster level accordingly.

The possibility of prestige classes that buff all 3 is especially odd in the context of Sorcerers; I see no reason to continue leveling Sorcerer once you qualify for a prestige class. A Sorcerer 10/Loremaster 10 character gets the same spells per day, known, caster level, HD, base attack bonus, and saves (actually, slightly better Will) as a Sorcerer 20, in addition to the Loremaster class features. (By contrast, Wizards get bonus feats, which they’d give up by pursuing Loremaster.)

I misunderstanding the rules somehow?