Online training has its place, & can be very effective (including cost) in some circumstances, and where appropriate. I've seen it done very well, for example, to roll out compliance training in financial institutions, to ensure that a geographically disperse workforce received the info they needed to comply with new legislation, and the organisation could also demonstrate that its people had achieved a demonstrated level of awareness.
But I don't think it's acceptable for training an auditor, and most particularly not a lead auditor.
Understanding the Standard? Yes, quite possibly could be done well online. But auditing? No, no, and no again.
Just for interest's sake, I followed up a link to an 'online audit training' site, and tried out a few of their sample courses. Now there's an hour of my life I'll never get back, & it was pretty much what I expected. Not impressed at all - very simplistic.