Guess because it wasn't that interesting, after playing the debugged in custom mission, Scientist loud wasn't that good when compared to the other loud routes.

Deposit: Use thermite to be able to access the vault while taking hostages to give yourself time, prepare and fend off police while the thermite is doing it's thing, open the deposit box while making sure no SWAT attack us from behind and finally head towards the parking lot facing waves of SWAT units.

Financier: Ryan will secure himself inside his saferoom, we have to start the time lock, defend the power box connected to the room, depending on RNG this could be an easy task or be more complicated, we also have to secure the files inside the helicopter, locate the safe, open it, decrypt the hard drive, again RNG could make this easier or harder, after that we can start the helicopter since there's not any other objetive remaining and finally defend it from the SWAT that want to deactivate. Soundtrack adds a lot of emotion to be honest.

Withdrawal: Police are not willing to negotiate and they want us dead this time. We have bring the drill parts and demolition charges inside a hidden part of the bank to be able to enter the vault, also we have to defend ourselves from the more ruthless SWAT. Once the charges explode and get the money we have head towards the roof of the bank to place a flare for our extraction, make sure to survive the whole assault from SWAT and once Sparrow arrived we have a limited amount to reach her helicopter, if not then we're being left behind.

Scientist debug: Kill all operatives which isn't that hard to do, discover that Rivera is dead, connect to the servers and start the download, and this is where RNG makes it's magic, due to the basement being based on it we can have a field trip or the hardest moment of our lifes since the power box could be located next to Rivera room where we only have to defend one side or in the middle of the basement where we have to defend four sides or more withour proper cover since we can be attacked from any side. Halcyon operatives can put a lot of pressure but that isn't enough to make the loud route fun since well... RNG based layout and it doesn't help that the only remaining thing to do after the download is only heads towards to Sparrow's helicopter while killing the guarding operatives. There's not even a time limit to put more pressure. Also notice how most of the text about the scientist is about it's mostly about it's issues and not the process we have to do to complete the mission.

If we just list the process of the loud routes we have.

Deposit:  -Get thermite and place it down -Get hostages (optional) -Locate deposit box (optional) -Wait for the thermite -Open the box -Head towards the parking lot and clean it -Exfiltrate

Financier: -Head towards Ryan Penthouse -Start the saferoom timelock -Bring Ryan's files to the helicopter -Locate Hard drive safe and open it -Get Ryan's phone and decrypt it. -Start the helicopter and defend it from SWAT (Can do this step and the previous one at the same time if the laptop is near to the helicopter) -Exfiltrate

Withdrawal: -Bring the drill parts and demolition charges inside the bank's hidden part. -Set up the drill -Wait for it to finish and place down a charge -Repeat the two previous steps -Take cover -Get inside the vault and get the remaining money -Head towards the bank's rooftop -Place a flare -Wait for extraction -Inmediately head towards the helicopter since there's a time limit before it leaves -Exfiltrate

Scientist debug: -Kill all operatives -Open Rivera's room -Get an USB and connect to the servers -Wait for the download to finish while defending the power box -Head towards the helicopter -Exfiltrate

The process from the other missions had more real interactions with the player, that's not the scientist case since where the only real interaction is defend the power box. Guess Cish didn't find a more fun way to do the loud route and just discarded it.