Willie, you are correct that this area of the receiver isn't heavily loaded in normal operation. You're also correct in surmising that the crack may not spread in further normal operation.
The thing that troubles me about your analysis and recommendation is that if a similar malfunction were to occur when shooting the cracked receiver, it may well injure the shooter, perhaps seriously.
We see that the receiver absorbed substantial excess/misdirected energy in this malfunction, protecting the shooter from the rearward exit of the bolt. There's no reason to believe further cracking will be progressive rather than a total failure.