[dns-operations] Someone on this list doing some empty non-terminal testing?

[David C Lawrence]

We're seeing some weird traffic that isn't really a problem, but was
peculiar enough to want to ask others about.

There's an AWS IP that has hit several dozen unrelated zones hosted on
us, specifically looking for a set of names under an empty
non-terminal.  The IP hasn't shown up in any other bad-actor
reputation data, and isn't a high volume of queries.  It is consistent
however in asking for:

(store|secure|www|ssl|mail).$EMPTY-NON-TERMINAL.$ZONE.

Anyone else seen this?