It's obviously impossible to prove a non-overlap (or overlap) between these groups from where we sit without more information, but I have a feeling that the people protesting the soldiers' prosecution do not want a ceasefire, even for selfish reasons.

Same people?

Entirely different groups of people, and they're profoundly opposed to each other.

At the core of this massive protest/strike are groups which have been against the bombardment of Gaza from the outset, and protesting Israel's war against Palestinians for years.

I really don't think these are the same group of people. From the article:

The strike was ignored in some areas, reflecting deep political divisions in Israel after nearly 11 months of fighting.

Those are the people you're thinking of, and they aren't striking.