The line about: “Think how bad it would be if Corbyn were in charge…” is only used (I assume) because his were the principles in the latest (2019) General Election Labour Manifesto. That makes them the general principles and positions of the opposition party (until changed).
If the Labour Party start telling us what their plans would be, if elected, then comparisons can be made with the current opposition. But such information does not seem to be forthcoming.