You’re still thinking about a point source, where the actual scenario is closer to two parallel plates, in which case the non-normal components cancel out, leaving only the normal component, except at the edges.

The most basic example from electrostatics: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.h...

I don't think the phone emits radiation from its entire body

That's what the cuts around the metal band of the iPhone are for, to segment the edge into different tuned antennas.

If you try to make an antenna too small compared to wavelength, it will become less efficient and more difficult to design. 900 MHz is the 33 cm band, so if you have a more standard size antenna on the order of quarter-wavelength size, you get an antenna that’s about 8cm.