Nah amazon is not attacking you 
Lets say a external ip tries to connect to you as a local subnet ip you often get this message because it is discarded because it sees it as a bogus ip or well more technically speaking it tries to override your dhcp/dns origin, also isps have local ips, and these should never talk to you and this mechanism prevents that.
Now in your case this could be related of using adguard or pihole then you have nothing to worry about if it was blocked the origin was changed to a local ip thus causing the origin mismatch, even with vpns this can sometimes happen.
Sometimes a device just uses it to reference itself as a reverse domain but intended for local use, but the dhcp server sees the origin mismatch and block it as rebind attack, again a false positive 
Tbh, aslong wan firewall zone is correctly setup only local devices would create such issue from device → isp and not isp → device, i won’t call it super dangerously to turn it off, i only would consider to advise to do not in public areas 
, well aslong it is possible, with things like captive portals you have no other option than disabling it.
Also it depends how recent the OpenWrt part is, but in luci inside the dhcp settings you can whitelist certain domains for rebind protection , and in the future it may or may not get added inside the gl ui, its still in the research.