I'm not familiar with the full history of the issue, but I think the idea of the eucharist being in a sense figurative instead of literal became more popular long after 325. In Nicea, during the proceedings, whether the body is literal as Catholics believe, wasn't an issue they were debating at the moment. If they didn't debate it, then there would be no reason for it to become part of the Nicene Creed. The creed itself would only cover issues that were being debated there. If there was agreement on an issue, or people were unaware of disagreement, then there's no reason to add it to the creed.

It's also possible at that time if there were disagreements, it didn't bother them as much, as they had much larger theological concerns bothering them than as to what the intention of the sacraments are.