Signal put forward the TLS-proxy as a way to circumvent specifically the block on signal. This suggests they want people to be able to access signal despite it

Signal put forward the TLS-proxy as a way to circumvent specifically the block on signal. This suggests they want people to be able to access signal despite it being illegal. The feature is 'use access in Iran despite it being illegal'. If that is your pitch, then 'being detectable as doing the illegal thing we want to enable' counts as a vulnerability for that feature. Whether software has a vulnerability or not cannot be determined without knowing how that software is meant to be used.