My guess is that it is either a bug or a restriction on how RegionEqual[] works with InfinitePlane[].
Here's a way to convert InfinitePlane[] to an ImplicitRegion[], on which RegionEqual[] works:
RegionEqual[
 ImplicitRegion[RegionMember[#, {x, y, z}], {x, y, z}] &@
  InfinitePlane[{5/Sqrt[74], -(7/Sqrt[74]), 0}, 
    {{-(5/Sqrt[74]), 1 + 7/Sqrt[74], 0}, {0, 0, 1}}],
 ImplicitRegion[RegionMember[#, {x, y, z}], {x, y, z}] &@
  InfinitePlane[{0, 1, 0},
    {{-(5/Sqrt[74]), 1 + 7/Sqrt[74], 0}, {0, 0, 1}}]
 ]
(*  True  *)
Note that RegionEqual fails on the simplest of equivalent InfinitePlane regions:
RegionEqual[
 InfinitePlane[{-1, 1, 0}, {{1, 0, 0}, {0, 0, 1}}],
 InfinitePlane[{0, 1, 0}, {{1, 0, 0}, {0, 0, 1}}]
 ]
(*  False  *)