Yes that is true, but that is not why he is asking. He has a new book coming out
Mythological Figures and Maleficent Monsters and I am guessing he is trying the gauge what CR the figures and monsters should be.
Yea you are right I did not want to lecture
@Morrus about the topic, he surely knows these things himself.
Still I think the CR thing in 5e is widely overrated and several CR classifications only apply for a certain party constellation and playstyle, that is for sure. For my group, consisting of Gen X people mostly they do not have the same playstyle that is e.g. portrayed by the pros at the South pax or whatever youtube videos.
I cannot explain it the easy way but I will try: E.g. if you watch those official sessions with chris perkins or so dm then its like : Oh the ravnica arena of bloody death and an npc is to be protected. Then the jim darkmagic guy casts his extradimensional hiding place above the arena and some one else or him uses a magical rope to secure the npc can enter it together with jim who then occasionaly blasts a magic missile from his hole into the ongoing fray. Dispel magic anybody (of the mobs)?
Or some other session taking place in some high up floating citadel, the number of acrobatic stunts requiring if at all a modest dexterity check, and sometimes did not even require a check if the dm found them particularly awesome.
It just is not happening that way at my table or in the round where I do play. I can be lucky enough if the DM gives me an opportunity to stealth. Lately we did have to climb a long rope ladder requiring us to make frequent acrobatics and constitution checks. I did complain about this to him, because I think one dex/str and one con check should be enough for such a task.
I hope I could point out what I intended to write, a mob with CR10 is trash for one group and nemesis of doom for another and it depends on so many factors that maybe CR is the wrong classification. You could as well write HD / caster / meat / heavy hitter / swarmer etc and it would be more helpful in selecting the right challenge.