Comment by Benjamin_Dobell

Admittedly I won't have time to go through the code. However, a quick look at the thesis, there's a section on multi-threading.

Whilst it's still very possible this was a simple mistake, an alternate explanation could be that each strip is allocated to a unique cache line. On modern x86_64 systems, a cache line is 64 bytes. If the renderer is attempting to mitigate false sharing, then it may be allocating each strip in its own cache line, instead of contiguously in memory.