The Milner point seems backwards: for an existing investor, cash is what they already have, and the presence of an existing investor means that their investment will be pre-diluted. If "runway" is all their startup needs, any investor would be happy to provide it.

The others seem right though, and really they all just come down to "reduced risk". The big problem for investors is that they have a hard time picking winners. YC and its community have a better track record.