H4 certainly sounds strange to me (and as other commenters have pointed out, this is a toy example, not a real molecule), but there are weird bond structures ou

H4 certainly sounds strange to me (and as other commenters have pointed out, this is a toy example, not a real molecule), but there are weird bond structures out there in real molecules that violate "at minimum, two electrons shared between the two atoms": https://en.wikipedia.org/wiki/Three-center_two-electron_bond https://en.wikipedia.org/wiki/Three-center_two-electron_bond. (The 3C-2E bonds in diborane are not linear, so that doesn't seem like what could be happening here.)