So if you generally had "search example.com" in you resolv.conf, and were in the habit of having "web01.dev" in places, behaviour may have changed if you were suddenly on a machine that had the "search" line missing (or something else).
What you describe is a user and resolver configuration problem. There are 100's of TLDs and there's always a chance they will conflict with subdomains, either now or in the future as new TLDs are created. I've been using both "int" and "dev" as subdomains since at least 2000 and never had an issue.
Lots of folks were using "dev" as a sub-domain which was fine until ICANN decide to give Google a TLD:
* https://en.wikipedia.org/wiki/.dev
So if you generally had "search example.com" in you resolv.conf, and were in the habit of having "web01.dev" in places, behaviour may have changed if you were suddenly on a machine that had the "search" line missing (or something else).