*sorry about the upside-down pics, I can’t seem to fix it. Anyone know how? They show correctly on my computer before uploading*

I’m posting again about my 1905 Toronto house. I’ll attach some photos of the top of the foundation. It is a 10″ CMU wall, which appears to be topped by a single row of bricks, placed lengthwise, with a doubled-up 2X6 set on top. The only reason I could imagine to add this row of brick is that they were too lazy to plan the wall height and ended up needing half of a block for the top. Instead of cutting the CMUs down to height, they finished with a row of bricks?

One small sectionof the bricks/mortar was in poor shape and I pulled 2 out. Behind I could see a row of medium-sized concrete blocks set on the inside edge of the CMU, which have a more traditional 2×4 placed flat acting as a mudsill. This will be shown below. However, the joists are not actually resting on this 2×4 “mud sill”, but are 1/8″-1/16″ above, and are resting on the outer 2×6 that is sitting on this row of brick. 

My theory is that at some point someone placed this inner row of block as a “backup mud sill” to support the floor joists if/when the 2×6 failed or settled. Does this sound plausible?

Does anyone know if this brick “mud sill” was a common building technique sometime in the last century, or am I just the lucky recipient of an amateur-builder?

Thanks!