It’s possible, and can be done at home. You need to literally freeze the RAM very quickly (typically with CO2) and transfer it to the new system. Then you dump the contents of the stick and hopefully find an encryption key.

From what i’ve read it’s temperature dependent, and at room temp some dram cells might take as long as 10 seconds to decay. The 64mS refresh is a super conservative call because it’s really bad when random bits go missing out of memory. The decay is faster at high temperatures, but some dram controllers might actually adjust based on temperature.