Maybe the mirrorless MFGs began with 50, 120, 200mm models and finally getting some quality 400 and 600mm lenses out there which are going to affect weight.
This is absolutely true. Check the release history for Olympus lenses - the 40-150mm Pro and 300mm Pro were two of the most recent releases. Both are relatively massive by micro-4/3 standards.
And the most recent releases were the prime f/1.2 pro lenses, which are seriously hefty and massive. The 25mm (50mm FFE), for example, is 410g. Contrast with the pancake Panasonic 20mm f/1.7, which only weighs 100g -- less than a fourth as much!
This is absolutely true. Check the release history for Olympus lenses - the 40-150mm Pro and 300mm Pro were two of the most recent releases. Both are relatively massive by micro-4/3 standards.