Missing `dtoverlay=pi3-disable-wifi` overlay?

Is MATE 16.04.5 missing the device tree overlay for disabling wifi? It was added to raspberrypi/linux 4.4.y branch Jan 2017 but I'm not sure how to verify in Ubuntu MatE. I'm running latest firmware:

lar@rv-server:~$ uname -a
Linux rv-server 4.4.38-v7+ #938 SMP Thu Dec 15 15:22:21 GMT 2016 armv7l armv7l armv7l GNU/Linux
lar@rv-server:~$ lsb_release  -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.5 LTS
Release:        16.04
Codename:       xenial
lar@rv-server:~$ cat /proc/device-tree/model 
Raspberry Pi 3 Model B Rev 1.2

Even though I added the overlay to /boot/config.txt and rebooted:

# Additional overlays and parameters are documented /boot/overlays/README

# Disable Bluetooth to reclaim UART for hardware serial port

# Disable built-in WiFi

## pps-gpio
##    Enable kernel support for GPS receiver pulse-per-second (PPS) input

the overlay isn't listed and no help topics are returned:

lar@rv-server:~$ dtoverlay -a | grep pi3
lar@rv-server:~$ dtoverlay -h pi3-disable-wifi
* No help found for overlay 'pi3-disable-wifi'

Just to be clear, there is definitely still a wireless interface:

wlan0     Link encap:Ethernet  HWaddr b8:27:eb:3b:70:ec  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:1987 errors:0 dropped:1987 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:784234 (784.2 KB)  TX bytes:0 (0.0 B)

Is this because the pi3-disable-wifi overlay is just missing?

Edited to fix formatting