UHND.com - Notre Dame Football, Basketball, & Recruiting

There was definitely time. And the DNC could have spent the money themselves on a diff candidate had they won more delegates at a convention. So the "not enough time" argument cannot be related to campaign funding.
This linked article is quite good, and it clearly shows that all of the money that was used by Harris could have been used by another Dem candidate who got more votes in the primary.

"Stephanopoulos: Let’s say Newsom became the nominee and there’s a bunch of money left over in the Biden-Harris account. That money could not go to Newsom directly, but it could go to the DNC’s account, which is separate from Newsom. And at that point, the DNC would also not be allowed to just give the money to Newsom. But the DNC could spend the money on its own advertising about how great Newsom is and that would be totally permissible. That would be independent spending. It wouldn’t be a contribution to Newsom’s campaign. At the moment, it doesn’t seem like this scenario will come into play. But if somebody other than Harris had been the nominee, that’s what would have happened."


Link: https://hls.harvard.edu/today/can-kamala-harris-access-biden-campaign-funds/