Mxsmanic wrote:

Why would they be more unlikely to cover solo flight in a twin? Is it
more dangerous?

yes. For a number of reasons already mentioned by others, i.e., there
are a lot more things that can get wrong, and the decision process is
more complex (stats I have seen suggest that you are more likely to die
if you loose an engine in a twin than if you loose one in a single);
more over, multi- aircraft tend to be bigger, faster, etc.

Even with a multi- rating it is not easy to find a twin that you
can rent on your own.

--Sylvain