The funny thing is that even in 3.5, the creatures with big lists of spell-like abilities (SLAs) were quite often not the combat monsters their CR presented them as being.
Sort of.
If you ever picked up a copy of Bad Axe Games'
Trailblazer: Teratologue (affiliate link) – which was a monster book companion to
Trailblazer, their own attempt at a 3.75 edition – you likely noticed that they made an interesting notation regarding the monsters' CR. Specifically, it noted that they'd used the work of Craig Cochrane (our very own
@Upper_Krust), who had taken the idea that a monster's CR was the aggregate total of everything in its stat block to its natural conclusion, devising an intricate breakdown that assigned a numerical value to each aspect of a monster's stats (i.e. Hit Dice, Base Attack Bonus, feats, skill bonuses, movement types, etc.), all of which cumulatively added up to its CR.
Now, the
Teratologue didn't reproduce U_K's work in full, but instead adjusted the monsters' CRs accordingly. However, it included a certain takeaway from it: all of the monsters in the book had their total CR, but also a "spine CR" listed.