Does it have True RMS?
No, although it has the same trick as a Fluke 27 up its sleeve.
If you look in the manual there's a table of correction factors for various wave shapes. eg. For a square wave you multiply the value on screen by 0.9.
Here's the table:
Now the trick. The Fluke 27 and 37 will keep on showing the
same value as the frequency rises, and
keep on showing it long after the readings shown by my Brymen 857 and Anengs and have all gone to hell.
eg. If I feed it a 3V square wave The Fluke 27+37 will show 1.66V on screen (ie. 1.5V/0.9) and keep on showing 1.66V as the frequency rises and all the others are starting to show garbage.
My tests show it will keep on showing the "correctly wrong" 1.66V up to 30kHz or more.
nb. I have a Fluke 8060A for measuring high frequencies - it's still the king of that even after all these years.