I consider it a upgrade, not having to rely on active power to get blown out into the vacuum of space. Just because you can do something the Fancy/Smancy way with force field, doesn't mean you should. Discovery was a "Experimental" ship and remember the USS Enterprise was experimenting with Holographics Comms until Pike ordered the entire system to be removed because of the interference they caused that brought down the rest of the ship. He also didn't like the fact that he felt like he was "Talking to Ghosts". I'm not a fan of the transparent Ghost like Holograms, seriously, just use solid Holograms like in ST: Nemesis, it's cheaper on the VFX department. I wouldn't be surprised that Pike ordered them to use a more traditional docking tube that doesn't rely on active power. I didn't notice, but I'll have to check for it next time I watch SNW. You are correct, they talk about that in "The Ready Room w/ Wil Wheaton". They went back to StarBase for repairs and are back out there to explore.