I don't think they're very different. I also don't know why you call them "monstrous" - the only sense in which they are monsters is the technical D&D sense, and in that usage angelc eladrin are also monsters.
They're "monsters" because the weakest has six hit dice, they're celestial beings surrounded by nimbus of light, can turn into whirlwinds, and shoot lightning. They're as akin to elves as angels are akin to humans.
Both sorts of eladrin are elven in nature. They are both nature/fey-inclined. (Look at the Ghaele's spell list on d20 SRD - it's full of animal and weather stuff. They also teleport without error at will, which is more often, and further, than most 4e eladrin can teleport.) Eladrin live on Arvandor, which is an idealised Sylvan plane, much like the Fewyild.
Which is why they went with that name rather than otyughs I imagine. It's easy to justify the faerie angels being the ancestors of elves.
But making them a PC race, renaming the plane, and generally completely changing the lore and background of the race is awkward.
For me, the changing of orcs from LE to CE - which happened in 4e - is quite a big deal, far bigger than putting the supernatural, celestial elves into a more consistent and coherent cosmological framewokr. But no one else seems to have even noticed the orc change, judging from the amount of comments I see on it (ie basically none). Which just goes to show that claims about degree of difference are relative to individual concerns and interests.
The switch from LE to CE happened in 3e. Or at least 3.5 (I don't have my 3.0 books any more.)
(Linking back to [MENTION=2067]Kamikaze Midget[/MENTION]'s post - when they announced the LE to CE change at the launch of 3E, they talked about how "we had all been playing our orcs as wild and chaotic, and so this change was just regularising that state of affairs". Well, I hadn't. For a long time I had treated orcs and hobgoblins as the same militarisitc, highly disciplined peoples. Does that mean that WotC were "insulting me" or "telling me how to have fun"? Not at all - they're just writing, publishing and marketing their game in a way that they think best suits their commercial interests, incuding the aesthetic aspects that feed into those commercial interests. I can do my own thing witout getting in trouble from them.)
Your example is minor. Tiny. You can ignore it by ignoring two small letters. It doesn't affect the portrayal of orcs in the past, change much of the lore, or affect your world.
But what if they had instead said that the differences between orcs and hobgoblins were too minor, that because people couldn't tell the difference orcs as we knew them never existed.
And they instead they introduced a new monster, let's go with the orog, that would fill the narrative gap left by the orcs. But now the orogs originated in the shadowfell. And that all worlds would now consider orcs orogs and have to retcon orc invaders as having originally come from the shadowfell.
That's insulting because they're telling YOU that YOU cannot tell the difference between hobgoblins and orcs because some theoretical person might have trouble. So rather than make it easier to tell the difference, they make the decision for YOU.