The main characteristics of options expiration days in terms of MF is the unusual activity in the last minutes of trading. We can see it on XLE for example. The Minute MF shows a spike at the EOD, but we can see that XLE had been very weak during the day. However, the XLE EOD Figure shows a positive divergence simply because only the value at the EOD is used.
Hence, traders who only use EOD values could misunderstand this positive divergence as "buyers moving in," while it is simply due to a very tactical short-term activity.
The 20DMF also shows an EOD spike.
Pascal