First I've seen of it. It certainly has some lines from a 1903 and a 1911, including the slide stop, but I don't know if there is a spring under it. The XD and XDm pistols have a spring-loaded slide stop. I understand that because the slide stop lever is so small and light that it needs to have the spring pressing it down to keep it from bouncing up under recoil. Maybe the Solo has the same issue.
I wonder why it has a mechanical safety. It is striker fired and looks to have a fairly long trigger movement, which seems to me to preclude the need for the thumb safety. Maybe it needs it to pass drop tests or something. I do notice that the trigger is not hinged like other striker-fired guns, such as Glock and the M&P.