New York, NY
? _forget_about_SRV_ ?
Well, and if, for whatever reason, the alpha8 is removed from service (died and/or under maintenance, etc)?
What if current ports have been changed there (via DNS SRV mechanism) by a load balancer or manually?
We have already more than enough customers who "hard-configured" even IP addresses/port combinations to say the least.
Any time, whenever anything happened - those customers are first to cry and curse that "everything just plain worked before then/that and then all of a sudden - it stopped and now nothing works; this is going to be CC who had destroyed my whole life, etc..." - all, accompanied by "whole package of things" related to a frustrated customer who posts to this site.
The OP clearly (!!!) and in multiple posts specified that their 3CX has NO problems working with "A" records - so why would they need to "test" some particular host-name/IP address which had NEVER been publicly announced to be used?
I suggest you to stay closer to your own system, customers and their configurations and stay away from providing "support" to posters who asked for help related to Callcentric and other providers' settings.
You have NO idea about how Callcentric (or any other provider's) system works, network topology and parameters (as well as - about 1000s other things in their network).
Please consider this seriously.