works!
Just picked up https://www.amazon.com/Samsung-T5-Portable-SSD-MU-PA500B/dp/B073GZBT36 at Best Buy and oh boy.
I'm always the first person into staging and have to wait for other people to join in. When I'm dropping in I can see the items on rooftops while I'm still in the air which helps with deciding on where on the roof I want to drop.
Other factors are that the skins in the game selection load near immediately (the gray placeholder is only there for about 1 second). Also if you hold down the PS button to go to party settings / friends, the lag is gone.
Here are the times from my PS4 Pro:
First # is seconds with default PS4 Pro HD, second is with external SSD (T5 Samsung) Game loading time from PS screen: 36 / 27 Blackout loading into staging: 24 / 11 Multiplayer loading map into specialist selection: 10 / 5
I recommend an external SSD to everyone. Set up time is 30 seconds to connect and select in PS4 devices, then it took 11 minutes to move COD to the SSD.