A single supernova could have collapsed a gas cloud and left Aluminium 28 on one side of the Earth . If there were many supernovae in all directions that gradually sent material to Earth then the Aluminium 28 would be found on all sides of Earth .
A supernova explosion that collapsed a gas and dust cloud to form the solar system wouldn't leave aluminum 28 on one side of the Earth.
The Earth would have to already be formed in order to receive aluminum 28 on one side. But the speculation in the question is about a supernova explosion collapsing a cloud and starting the formation of the Earth, a process which no doubt took many millions of years.
If a supernova explosion started the collapse of the cloud of gas and dust which formed the solar system all the atomic nuclei of aluminum 28 would attach to orbiting grains of dust or else orbit around the center of mass of the condensing gas cloud.
And of course the closer an orbiting gas molecule or grain of dust was to the center of mass, the faster it would complete one orbit around the center of mass.
So some particles which eventually winded up on Earth would take days to make one orbit around the center of mass, and others would take centuries or millennia to make one single orbit.
And it would take millions of years for atoms and molecules and grains of space dust to clump into somewhat larger particles, and those to clump into larger objects, and so on and so on. Eventually objects kilometers or miles in diameter would be colliding and sometimes sticking together to slowly build planets.
And during that time some particles of aluminum 28 which eventually found their way into the forming Earth would orbit the forming Sun thousands of times as often as some other particles of Aluminum 28 did. The particles of aluminum 28 would be thoroughly mixed in the collapsing nebula long before Earth formed. The idea that particles of Aluminum 28 would be more common on one side of the nebula which Earth formed out of is false.