Scott R. Moore of Galaxy Comics in Saginaw, Michigan saw the comments by Jay Bardyla of Happy Harbor Comics on holiday shipping (see 'Jay Bardyla of Happy Harbor Comics on Holiday Shipping'), and feels that the impact of holiday delays is minimal: 

Bardyla said:  'The Canadian holiday on May 21 delayed Canadian retail release dates by one day, from Wednesday to Thursday, but had no impact on American retailers.  However, the American holiday on May 28 ALSO affected Canadian retailers by one day even though the American holiday had zero impact on shipping schedules into Canada.'

This is just a guess off the top of my head but I think it worked something like this: Diamond ships product to Canada normally for the week of May 21st but, due to the Canadian holiday, delivery gets pushed back one day.  That doesn't affect US customers.  Diamond ships product one day late for the week of May 28th (because UPS is closed, if not Diamond) and that pushes delivery back one day for everyone.

It may not be 'fair,' but it is what it is.  Diamond is going to ship product to everyone on the same day, holiday or not.  However, I don't see how it will take 'weeks to recover from the disruption.'  Whenever we have books delayed for a holiday, bad weather, UPS mishap, etc. it takes a week to recover.  When the following week's product is put out on Wednesday none of my customers remember (or care) that books were a day late last week.