I don't think with Hermes/Evri theft from the depots is a major thing.
I think it's simply that they don't have the staff, or the infrastructure to deal with the volume of packages they deal with, and the management are dishonest about it and blame "theft" when in reality a lot of it is that packages are sitting waiting for a "quiet" day that might not come for months.
Even before covid it wasn't unusual for a Hermes package that was meant to be 3-5 days to take 7+ working days during "normal" periods, let alone at Christmas (which it turns out comes as a surprise to the people in charge of making sure Hermes had enough staff).
Assuming the companies that use hermes/evri get the cost of the packages that are "lost" back, i suspect that hermes/evri must lose an absolute fortune in compensation every christmas simply because they don't have the capacity to deal with the packages they're accepting and won't admit it to the companies using them, so customers waiting for packages are then chasing it up.
I also remember when we had the bad snow that was causing disruption, and hermes from memory basically said "***** it" and handed millions of packages over to RM to deliver, knowing that RM couldn't refuse them (and that RM were struggling themselves due to the weather). It said an awful lot about the business plan for them as a courier that their backup plan for being unable to cope was to pass offload their responsibilities onto a third party at no notice.