[noise] Noise handshake pattern validity question

[Matvey Mukha]

Hello,

Can I please ask a question about Noise handshake pattern validity?

I'm looking at the validity rule number 4 and the four cases it
outlines. If we take case number 3, "After an 'es' token...", what is
the reason that the case cannot be safely extended to say "...unless
there has also been an 'ee' or an 'se' token"? Would not it still
fulfill the general description of rule number 4?

In practice, if we take the IX handshake pattern:
-> e, s
<- e, ee, se, s, es
What would be the negative effects of removing 'ee' from it?
-> e, s
<- e, se, s, es

Thank you for the Noise Framework!

-Matvey