A party does not fail to respond because it believes the other side will win on its own. Further, the "goliath" theory doesn't apply when the judge (and not a jury) is resolving this issue. The judge will not look at it in that regard.
In addition, if Ericsson failed to respond, while not an indication that Ericsson consents to releasing the docs, it does imply that Ericsson is not adamantly against it either. Thus, failing to respond does not maintain the status quo, but rather hurts IDCC's position.
There are only 3 potential scenarios here:
Ericsson responded and its not on PACER (less likely)
Ericsson decided not to respond
or
IDCC and Ericsson are filing a joint response (less likely).