Parallax occlusion "seam" between blocks with block variations.

Hi! I've been searching for a while about a peculiar quirk, and I'm not sure if it is intended or not, so I've come here. Is it a known issue that parallax textures don't work well with block variations? Using Iris 1.8.5, BSL shaders (And also complementary), and the resource pack SPBR, there might be a "seam" between two parallax textures on textures with block variations. It's like the "right" texture is expecting another variation of the "left" texture, but because of the mismash it doesn't work sometimes. A friend of mine using similar mods (not sure of the version numbers) also has this issue. I'm on linux with AMD GPU, and he is on Windows with an Nvidia GPU.