Part of the problem these days is that rail and tube passengers and staff in London especially have been mentally conditioned to think any unusual bang, unattended bang is a bomb first and anything else is a secondary consideration.
Shame there was no video of it, but that pic does look quite bad and wonder if it is partly a camera angle. looks like the major part of the flash was between the front cab on the blocks and the barriers.
suppose we'll have to wait years for the raib report, though i'm sure it will be thorough as usual.