Minecraft wiki entry for What_the_Far_Lands_are_not, associated text: Noticing that the precision loss is a gradual change, which increases at each power of 2. This is in stark contrast to the Far Lands, which happen immediately due to integer overflow.
Backporting a Superflat world (with flat terrain where the Far Lands would be) from 1.1 to Beta 1.7.3, and noticing that the effect persists in said version, proving that it's clearly not linked to terrain. While Far Lands chunks will still generate outside of what superflat chunks were generated in 1.1, these still are unrelated.
Modding the game can be done to either patch out this precision loss issue or the Far Lands individually. This proves their existence to be completely independent.
Generating the Far Lands in any version between the March 27 and June 18 builds of Infdev inclusive. Whereas the Far Lands clearly generate in these versions, the precision loss bug was first introduced in the June 24th build.