Why would the height and size matter if you're asking what their job is?
very small by my stands
This in a thread about "small" forwards should've given it away.
I don't know that Sobey is a small forward either. He's been a guard for the 36ers.
Their job is to be effective. Not every player at a given position fits a stereotype. There are classic, effective undersized power forwards. Or scoring centres, or defensive centres. Scoring point guards. Shooting guards and defensive off-guards. Small forwards that play a defensive role or 3&D or are power hitters.
Defence is useful, perimeter shooting and/or penetration are useful, versatility in guarding multiple positions is useful.
If someone has small forward skills but is 5-6" taller, they're generally playing in a better league.