TinyMCE custom styles not working inside PropertyList

I've a block, which holds a property list, and one of the property list properties is an XHtmlString, which invokes the TinyMCE control on the front end, but the list of styles that is present in the rest of the site's TinyMCE's are not present for the property list property.

Example with Screenshots:

Block has an XHtmlString property, TinyMCE has picked up the custom styles with no problems...

PropertyList on the Block... XHtmlString's TinyMCE has not picked up the custom styles. 

Is there special requirements for get TinyMCE to pick up the styles?