There are a number of instances where actions taken by ICANN need the support or consultation of the Registrars Stakeholder Group. Without someone from ICANN coming on here and confirming officially the reason for the duplicate records I suspect that it could be similar to a shareholder type of situation where each accredited registrar entry has one vote and the more entries the more effect you can have on the direction of ICANN.
I admit this is a hypothesis but from my basic reading of the ICANN bylaws it looks to be that could be a big factor in it. I would say it also has something to do with protection against de-accreditation but I would say it is probably less to do with that than many people think as it would be a simple matter for ICANN to de-accredit all entries a single entity has (such as what enom has as obvious duplications). As for a large number of entries which trace back to NameBright these d appear to be deliberate attempts to circumvent any grievance or de-registration measures as these companies are listed as partners of NameBright and that is all they do.
It may also be possible that at some time in the past there really was a company named Echo Domain which was bought by NameBright and amalgamated as well as amalgamating their ICANN accreditation.
I would say that all of these cases could be seen in the ICANN accreditation list and I have to say it is highly doubtful all duplications are attempts at using a loophole for re-accreditation protection.