@neongod Even if you allow access to your contacts, they will not leave your device. What happens afaik is that a hash sum is being computed from each contact and only that is send to signal servers, so that they can know (in an anonymity-preserving way) who of your contacts has #Signal so that you can talk to each other directly. So yes, they need access to your contact, but it is not the invasion of privacy that you seem to be making it out to be.
Look here for a description of the hows and whys: https://support.signal.org/hc/en-us/articles/360007061452-Does-Signal-send-my-number-to-my-contacts
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