This announcement was made very shortly after Trump started making claims that a vaccine could be ready "late October/early November". Trump is a known fool, and even were he not, his losing prospects at re-election, combined with the criticism of his administration's response to the pandemic make it seem like he could be pushing vaccine makers to rush a treatment to pump up voter support.
I believe vaccine makers are diplomatically responding to the Trump headline by saying "We aren't going to rush this for the wrong reasons."
I'd rather more people die to Covid than find out 20 million people have failing livers and 5 million were born with birth defects because they rushed a vaccine without enough testing.
The bigger issue is if they rush a drug that does long term harm to people, it could destroy the company. This is a drug that they will be giving out to 300+ million people in the US along. Screwing it up would result in a massive amounts of lawsuits that they may not recover from. They don't want to risk that just for some political capital with a person who may not be in power in a few months.
I feel like ending the pandemic is not a motivation that is likely to make a researcher (an expert) rush things and end up hurting more people. Greed or glory is much more likely to be a motivator for that kind of mistake.