I can't see what one would gain by building a S&G first. Both construction
methods are so different that no essential skills are learned by building a
S&G first and a strip-planked kayak later. Well, if one doesn't have the
patient to finish a S&G than it would be hopeless to start a strip kayak, but
that has nothing to do with skills.
To get an idea how strip planking works and to discover little tricks a better
approach could be to built a model boat first, such as a 3 foot sailboat hull
or a scale model of the kayak.

ulli