Right now, you can try resolving common hosts, and you will see that they often provide several hosts in response to a lookup. What the browser does with those IPs is up to the browser, the standard does not define what to do. What the administrator that sets up that record wants is "send to whichever one of these seems healthy", and some browsers do do that. Other browsers just pick one at random and report failure, so your redundancy makes the system more likely to break.
What I want is a way to define what to do in this case. Maybe you want to try them all in parallel and pick the first to respond (at the TCP connection level). Maybe you want to try them sequentially. Maybe you want to open a connection to all of them and send 1/n requests to each. Right now, there is no way to know what the service intends, so the browser has to guess. And each one guesses differently.
(You will notice that people like Google and Cloudflare skillfully respond with only one record with a 5 minute TTL. That is so the behavior of the browser is well defined, but it also eats their entire year of 99.999% uptime with one bad reply. Your systems had better be very reliable if DNS issues can eat a year's worth of error budget.)