It looks like the information at the bottom of the PTR record info page is incorrect. It appears to be copied from the SOA record page.
Specifically:
The value here represents an email address ,which can be confusing because it’s missing the ‘@’ sign, but in an SOA record…
There is also a typo on both pages in that quote. Specifically the comma at ...email address ,which...
Not sure if this is where I was supposed to post this so apologies if I got it wrong.