The bed thing is real, but I think you're also describing something else that's worth naming: passive studying. Six hours reading on your bed with zero retention isn't a study session, it's time spent near a textbook.
When I was prepping, I had a week like yours around month one. I thought I was putting in the hours. I wasn't. I was just... present in the same room as GMAT material.
Two things that actually helped me:
First, yes, move to a desk. Library, coffee shop, doesn't matter much as long as you associate that space with focus. The sleep-association thing your article mentioned is real neuroscience, not bro-science. Your brain genuinely gets confused when the same pillow where you sleep is where you're also doing Two-Part Analysis problems at 11pm.
Second, and this is bigger: the focus problem you're describing usually isn't about the environment. It's about the session structure. When I switched to timed 35-minute blocks (one section's worth of questions), then a 10-minute break, my retention jumped noticeably. The GMAT is a timed test. Training your brain to operate in focused bursts that mirror the actual test format builds mental stamina over time.
Two months is enough time. I've seen people go from panicked to 700+ in that window. But those people stopped spending 6 hours near GMAT content and started spending 3 hours actually fighting with it.
Start with one official practice set tomorrow, timed, at a desk. See how different it feels.