No, not all allegories, or any other literary device that is used in the Bible, states that fact prior or after utilizing the convention.
When Jesus said 'eat my flesh, and drink my blood', or 'sever your body part if it offends you', did he state a caveat for those two verses, as in , '...these expressions are just figures of speech...'. Or, do you take them literally also (rhetorical)?
And like I said, Jesus did rather overtly and blatantly indicate that this is an allegory, by the entire implausibility of the environment, and dialogue.
Not to mention, eschatology was not even the context for Jesus' remark, it was about the imminency in accepting the faith while on earth, for there will be no other opportunities to apprehend it after death, nor excuses as to why you didn't while still alive.