Tolkien actually never equates these terms (that I'm aware of), but you may be noting this on certain websites. The reason for this would seem to be: in the same explanation (published in later editions of
The Hobbit, as noted) that reveals 'goblin' has been used to translate
orc, Tolkien adds: or hobgoblin for the larger kinds.
Somewhere (in a letter I believe) I think Tolkien noted that 'hobgoblin' should probably refer to smaller kinds! but he had already published this in any case, to explain the use of this word in
The Hobbit, which
I think only occurs once. Thus some are equating hobgoblin or 'large goblin' with Saruman's 'larger' goblin soldiers.
And the statement (currently on Wikipedia):
'Tolkien then renamed them [Hobgoblins] as Uruks or Uruk-hai in an attempt to correct his mistake' is someone's opinion, the 'mistake' referring to Tolkien's statement in a letter. To my mind this really needs no correcting in any case, despite any external factors. If 'Hobgoblin' refers to larger kinds
within the context of Middle-earth then so be it (in my opinion).
Note again that, despite this explanatory note appearing in
The Hobbit it was added to a later edition, so JRRT had not published 'hobgoblin' for 'large goblin' until
after he had published a tale in which the
Uruk-hai appear. Tolkien would hardly rename Hobgoblins
Uruk-hai to correct a 'mistake' he had yet to make.
What the
Uruk-hai really are is quite the debate, but anyway
if you are thinking of the word Hobbit (and you need not be of course): internally, yet with reference to an invented translation,
Hobbit comes from 'holbytla', so the altered beginning of 'Hobbit' relates to the meaning 'hole'.
Even though a Hobbit (a kuduk) is a halfling (banakil)!
It's nicely confusing
