This is correct, because you are setting the specific proxy you are connecting to which is sip-byod.voipwelcome.com (regardless) of what your proxy setting is set to, unless you are one of the VOIP old timers.
This is simply a registrar server however which is just a server that maintains your registration state, there is a lot more that goes into the infrastructure however as far as call termination and origination.
Hopefully this gives you a bit more clarification.
Thanks and have a great weekend!
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