you'll see that IO::Socket::INET behaves the same regarding EINTR

Right, but those are two completely different beasts: IO::Socket::INET is just a thin wrapper around the networking support provided by the kernel. On the other hand, IO::Socket::SSL implements a full and complex protocol on top of that. It even allows you to pass callbacks for customizing the connect behavior. Restarting a TCP socket is cheap and doesn't have visible consecuences for the user while restarting a TLS connection may require some repeated interaction with the user, as for instance, accepting certificates.

Besides that, signals showing up while inside IO::Socket::SSL will turn into EINTR errors only when they catch the module inside a blocking syscall which, as TLS has a significant computational cost, may be quite less often than in the IO::Socket::INET case. So, depending on EINTR may be quite unreliable anyway and so useless.