Can they determine from those shards whether they contained wine or wine vinegar? A great deal of wine was made for vinegar in those days for medical and other antiseptic purposes and it was and is quite effective.
They would have made vinegar, but when an armed cohort wanders in, thirsty from the field, best approach is to serve the freakin’ wine. :’)
Vinegar was one of the barter items Roman soldiers rec’d as pay. The other was salt.