The Standard Services link on the Arduino BLE web page is broken.
It looks like Bluetooth dumped the bluetooth.org domain used in that link and the redirect to bluetooth.com is no longer working. I used Wayback Machine to find the correct redirect from before it broke:
Assigned Numbers | Bluetooth® Technology Website
@cmatt, please report this error to Arduino support:
Make sure to provide the URL of the reference page that has the broken link, as well as the updated URL I provided above. Thanks in advance!