i've seen couple of shyvanas with smite and TP top at diamond

A pro did it once to grab Cinderhulk.

While apparently forgetting that Sunfire Cape exists.

There's a couple reasons i can think of...

quickly solo a camp before getting to lane with the machete for gold/xp advantage

double smite ensures secure objectives

if you can roam from lane you can use that roam to counter jungle effectively

upgraded smite can bring some utility (chilling or challenging)

It was played quite a bit in the LPL, where they started Ruby Crystal into cinderhulk into Challenging Smite w/ Cinderhulk. They were also 100% lane swapped so shyvana afk-farmed the jungle, then caught minions at the tower, repeat ad nauseum. The Shyv just got rediculously ahead in CS compared to the other top laner.

I've been wanting to try it on Shyv, but haven't been doing many normals, I like the idea of a laner taking Smite for securing objectives.

hold up

doesn't this mean ANY top laner can do the same? or is it something exclusive to shyv?