XMP, an Intel invention to place essential settings for a memory stick in firmware to aid BIOS in setting essential (not all) parameters for best tested frequency, latency etc. for given RAM stick(s). It's NOT overclock by any means, just best settings for RAM to operate at it's highest rated speed. BIOS itself is not obliged to use all the XMP settings but may do some variations.
JEDEC is industry wide standard, while XMP is not. Intel systems tend to stick more closely to XMP while Ryzen systems are more loose with settings.
There is another component to RAM, it's IMC (internal Memory Controller) inside modern CPUs, they all have either locked or unlocked highest frequency of particular (for that model) and only if you "overclock" RAM is higher than that value can be considered overclocking of RAM. Some RAM may have 2 or more XMP profiles and all have several JEDEC standards. It's also not true that all RAM have lowest frequency at 2133MHz, there are lower and higher ones.
Take a look at my setup for instance. RAM has XMP profiles for 3000 and 3600MHz, lowest JEDEC shows 667 (1333)MHz, BIOS starts it at 2400MHz on auto but can be lowered.
XMP calls for Cl15 at 1499MHz, DOCP sets it at VL16. XMP for 1802MHZ at CL17 while DOCP sets it at Cl16 again.
Now I have a crazy combination in BIOS,DOCP set to 3000MHz Cl16 but frequency manually set to 3600MHz also at Cl16. BTW, 3700x IMC's best frequency is 3200MHz. So yes, memory as far as IMC is concerned is overclocked but RAM itself is not. It's running at its projected best frequency with some "fixed" Cl and other values.