To be or not to be ... is not a question in the invented language of E-Prime. TopTenz explains:
Another language constructed to make a philosophical point, E-Prime is simply a version of English that forbids all forms of the verb ‘to be’ (is, was, were, etc).
According to Alfred Korzybski, who promoted the language in his 1933 book Science and Sanity, E-Prime can be used to sharpen critical thinking and make ideas clearer. For example, in E-prime a person can’t say ‘This is an awful movie’: it must be rephrased as ‘I dislike this movie.’ ‘You’re wrong’ is also impossible: instead he must say ‘I disagree with you.’ Because of this, it’s easier for speakers and listeners distinguish fact from opinion.
On the other hand, following E-Prime to the letter becomes burdensome: ‘This is a flower’ must become something like ‘English speakers call this a flower.’ Today, E-Prime remains popular, but mostly just as an interesting thought exercise to improve clarity.
Read more about the Top 10 Invented Languages: Link
E-prime makes you take responsibility for what you say. Rather than saying, "He's a jerk," you have to explain why you dislike the person in question.
Having been away from academe for more than two decades, though, I've gotten out of practice.
All of this seems to indicate that there was no concept of a set to contain all sets, or terms that refer to a universal set or the bare fact of existing. These were not common ideas at the time these texts were written. But they may have been ideas which the texts attempt to describe in different ways.