If survival is the endpoint and they just confirmed the triggering event, they have all the necessary data in hand*. And I'm sure they have computers.
1 week. Max.
In theory I would agree that most of the data checking could be done in real time - however it is human nature, now that the data is available to another set of eyes (the trial sponsor), to double check before such a make or break event as an analysis that could be used for submission (the FDA doesn't allow go backs). Do you even know of a company that processed an interim that could be used for submission in 1 week?
leave investors open to disclosure shenanigans
The data is still blinded. It is possible to infer the arm in some cases - but generally I haven't seen any evidence (in stock price movement) that that is a rampant problem.
PS On your larger point of companies not releasing data, I agree that companies are outright flouting the law right now. Literally the only company I have seen release results, as per the law, on clinicaltrials is Inspire. (There are probably others, but out of 30+ companies I've looked at only Inspire obeyed.). Looking forward to the first lawsuit against a big pharma
I spoke with a company in the obesity space. They told me they held off releasing data because it takes a long time to get quotes from investigators for the press release. Sat on the data for a month. I was pretty stunned.
IMNSHO they do it to allow anticipation (and a nice PPS runup) to happen... Remember that most bio investors are hopeful. IMO the baseline emotion in bio traders is hope. And they can exploit this by waiting.