I think that they estimated that date some time ago as it was going to be 100 years after Gaudi’s death. However, due to COVID and less tourism following restrictions, they have delayed the completion a few years. The following link explains it, though in Spanish. 

https://visitarsagradafamilia.com/sagrada-familia-terminada/

Plans are to complete Jesus’ tower by 2026, which will be the tallest one in the cathedral (172 m)

I heard most would be done by 2026 for the anniversary. They have made a lot of effort in the last few years

carlosfandango

Yes, according to latest information they are planning to finish it around 2033. 