On a side note, it looks there is a second OLPF in the 5DM3.
Yes and no. The confusion comes from the fact that what we call the 'anti-aliasing' filter actually has two components that are essentially polarizers, one oriented horizontally and one oriented vertically. The two filters are separate within the assembly, with a 1/4-wave plate in between (necessary to convert the linearly-polarized light from the first filter into circularly-polarized light, else no light would get through the second filter, like when you orient a pair of linear polarizers at 90° to each other, the same principle that variable ND filters use).
The horizontal layer of the AA filter, 1/4-wave plate (what Canon calls the 'phaser layer') and the IR cut filter are bonded together, and this assembly is what vibrates for the 'self-cleaning sensor'. The vertical layer of the AA filter is bonded to the sensor itself (well, on top of the microlens array, which sits on top of the Bayer mask, which sits on top of the sensor).