Here's my opinion about weapon holstering in Fallout 4:
In Fallout 3, many of my weapons just levitated off my hip or back. That drove me nuts and then there were some weapons which vanished upon holstering, regardless. Flamer, Minigun, Gatling Laser, pretty much all Big Guns.
I understand that there were reasons for this and I'm not complaining, just pointing out.
Then in Skyrim, the quiver for your bolts/arrows almost always levitated about 5 inches off your hip or back unless you were wearing the bulkiest of heavy armor. Most quivers didn't even sit correctly with the outfit they were designed for.
This bothered me to the point that I only kept my bolts/arrows equipped in first person and would switch to a different weapon in third person.
To summarize, if Bethesda felt as though they could not execute this feature without making it look like weird like it did in Fallout 3, Fallout New Vegas and Skyrim, they should scrap the visible holstered weapons.
PS. I also want to mention that your stuff 500 Stimpaks, 256 Prewar Money, 10,000 Bottle Caps, 3 Suits of Recon Armor, a Baseball Bat and a Sniper Rifle into the computer on your arm. I think the disappearing holster should be the least of your concerns.