The Ideal version of Wagos ("In-Sure") are listed for stranded wires.
Use of Wago-type connectors - including this new gizmo- on short wires in existing work is tempting, but problematic. The only failures I've had with the connectors has been when the bare wire had been previously used for connection, and was bent or nicked.
King makes small set-screw connectors that are listed for use with aluminum. Thomas & Betts has a line of "Marettes" (wire nuts) that are listed (CSA, not UL) for use on aluminum. (T&B may choose not to market them in the USA, but they are available).
As has been discussed here several times, 'back-stab' devices might appear to work like Wagos, but what's inside is often quite different. This seems to explain the difference in reliability.
