ME/CFS has quite little social recognition. So people don’t often “pretend” to have it because it’s not on people’s radar’s like ADHD etc is.
The problem though is people often assume lots of “hypochondriacs” have that condition, because the name “chronic fatigue syndrome” doesn’t sound very serious, (nearly all patients prefer calling it ME or ME/CFS) but that stereotype basically means people with the condition are constantly accused of faking and stuff and it’s just a horrible all round situation.