Precision 3620 RAM speed vs. CPU

This might be an easy one, but I couldn't find an answer.

Dell says 7th Gen CPU only supports 2400Mhz RAM.

Intel says their i5-7500 supports both 2133Mhz and 2400Mhz.

I have both on the way, a Precision 3620 and an i5-7500.

Is what Dell says a Dell limitation, or does the the i5-7500 support both speeds in a 3620?

From the 3620 Tech Guide:

From Intel for the i5-7500:

I'm also looking to add RAM, but don't want to screw it up, even though I can return it.