This is something interesting I hadn't heard about. Anybody have more information?
# Release 3.3.5 - (May 9, 2019)
~
* Testnet: there is now a warning when the client is started in
testnet mode as there were a number of reports of users getting
scammed through social engineering (#5295)
~
The full discussion about the issue is in the Github page:
#5295.
Apparently, it's all about "
social engineering" cases of scams where the scammers are sending testnet versions to greedy newbies to convince them that they have doubled their bitcoins.
Though testnet version is obviously visible on the title bar, a warning is much more comprehensive to newbies to understand that "
it isn't real bitcoins".