The IPv4 address listed on that page works fine, and the traceroute back to me works fine too. So it mustn’t be using the same path as the monitoring station.
I’m also experiencing issues getting to some ISPs in the London area, so I’m relatively confident this is a problem with one particular US/NA ISP reaching my ISP in AU.
No problems for IPv4 or IPv6 seen from my main monitoring client, reachability was good. I did notice that the reference ID changes at about 2019-07-10 10:00 UTC from an Apple NTP server to an RFC1918 address. At this time root delay dropped from ~18 msec to 1msec. Neither of these should hurt the score.
In limited testing from my own machines, some of my machines can ping 150.101.186.48, and some cannot. For those that cannot, the traceroute stops at ppp178-79.static.internode.on.net (150.101.178.79), which suggests to me that packets are likely getting to 150.101.186.48 but the responses are getting lost.
Yeah - that was just me fixing my local stratum 1 server’s kernel, on which I broke the kernel a few days back. The Apple servers are there as backups for exactly this circumstance.
I’m not getting the routing problems you’ve described, but I’ve had them at another NTP pool member I have on the Telstra Business ASN, so I share your suspicions about the US monitoring station’s ability to reach Australia reliably.