This is a direct consequence of the change to the gardening system that was made in that update (UPDATE: 06/19/2018 – PC 1.44.77.1020 / Mac 1.44.77.1220). Prior to that update, plants could produce harvestables at any time of day and did so whenever they finished their growth cycle and/or harvest cycle. All the plants at the Science Lab could be harvested, including the wild plants outside the lab.
After the update, plants only produce harvestables during the hour between 5 a.m. and 6 a.m. (except for the plants spawned by the City Living festivals) and you have to be on the lot for that to happen. That made it impossible to ever get a harvest at the Science Lab.
The Scientist career doesn't start work until 10 a.m., which is much too late for the daily harvest cycle. The work shift ends at 7 p.m. It is possible to work late, but that only adds a couple hours and you still have to leave the lot long before the next harvest cycle begins at 5 a.m.
There doesn't seem to be any way for Sims to visit the lot outside of their work hours, which means that the daily harvest cycle never takes place on that lot. That's why it never has any plants ready to harvest.
