My guess is that such a vaccine would take longer to develop, but I'm not sure about that.
Wiki also lists the following drawbacks:
In rare cases, particularly when there is inadequate vaccination of the population, natural mutations during viral replication, or interference by related viruses, can cause an attenuated virus to revert to its wild-type form or mutate to a new strain, potentially resulting in the new virus being infectious or pathogenic.[34][39]
Often not recommended for immunocompromised patients due to the risk of potentially severe complications.[34][40][41]
Live strains typically require advanced maintenance, such as refrigeration and fresh media, making transport to remote areas difficult and costly.[34][42]
The study that you are referring to took place "Between July 27, 2020, and November 14, 2020". The delta variant started in India in late 2020 and wasn't spreading widely within the United States until 2021. It was listed as a variant-of-concern by the WHO on May 31, 2021.
So the research you are referring to is in regards to other variants of sars-cov2
https://en.wikipedia.org/wiki/Attenuated_vaccine
My guess is that such a vaccine would take longer to develop, but I'm not sure about that.
Wiki also lists the following drawbacks:
In rare cases, particularly when there is inadequate vaccination of the population, natural mutations during viral replication, or interference by related viruses, can cause an attenuated virus to revert to its wild-type form or mutate to a new strain, potentially resulting in the new virus being infectious or pathogenic.[34][39]
Often not recommended for immunocompromised patients due to the risk of potentially severe complications.[34][40][41]
Live strains typically require advanced maintenance, such as refrigeration and fresh media, making transport to remote areas difficult and costly.[34][42]