Hah, we commented on the exact same paragraph within a minute of each other! My memory agrees with your memory, although I think that should be 3E 00. Let me look that up:

https://jnz.dk/z80/ld_r_n.html

https://jnz.dk/z80/xor_r.html

Yep, if I'm reading this right that's 3E 00, since the second byte is the immediate value.

One difference between XOR and LD is that LD A, 0 does not affect flags, which sometimes mattered.