I don't think this is the same. `Dynamic` is an object along with its reified type. Now consider a dynamically typed function that returns either a String or an Int, according to a Bool parameter. This function ought to be statically type-able as Bool->String OR Bool->Int. It does not have a single static type, so it cannot be represented as `Dynamic`.
I went back to Siek & Taha's original formulation and they have a nice examples section in 5.3 of some interesting higher-order cases with Dyn, that better demonstrates than my clumsy attempt.
http://www.cs.colorado.edu/~siek/pubs/pubs/2006/siek06:_grad...
`Any` is also often called `Dyn` or `Dynamic` in normal typed languages, which is slightly different to `Any` here (core.typed's `Any` is the supertype to all types, `Dyn` is usually both the super and subtype to all types).