Both by RAW and Probably Intention They Normally Cannot
Obviously the Stat Block says what the Stat Block says. However we can find a bit more possible evidence of intention in the introduction to another official module (flagged as spoiler because we are trying to hide the creature, not because it is a spoiler for the other module):
We can look at the very first paragraph of the introduction to the Storm King's Thunder module, which shared some of the same design team.
On page 7 it says:
Because giants figure prominently in the story, at least one character should be able to speak and understand the Giant language.
Obviously this is not a definitive statement on the subject, but it indicates that WotC (or at least someone there) intends for the monolingual limitations of this creature to at least sometimes provide actual encounter or story challenges. This is an assumed game mechanic mentioned in the very first paragraph of this other official WotC module, so it is probably more likely to be an indication of general WotC philosophy towards this creature's linguistic skills interacting with players as anything we are going to get.
Changing This is Very Unlikely to Break Your Game
Only a very poorly designed module would require not being able to communicate with a creature such as this one.
This is because some player characters will actually speak this creature's language, either by choiceas a language they chose in character creation or as a racial ability. If the party not being able to communicate with them was central to the adventure then this would be a serious oversight. Similarly there are magic abilities which allow various sorts of communication through unknown languages, which once again is going to potentially break anything which hinges on them not speaking common.
In the end it is the DM's choice. It eliminates a potential limitation for some parties, but it is a limitation that would frequently be absent anyway, so it can hardly break any well designed module. It is likely an intentional limitation, but not necessarily one you are interested in featuring.