DNA evidence does not support Lt Col Isaac Allen as my 4th great grandfather. I'm currently chasing Dow the McCartys of Virginia and New Jersey who migrated to Indiana and Tennesee.
I have a theory about Samuel McCarty's name and birth. When Sabinah and family left New York in 1783, Sam was already 5 years old. No surnames were listed. The Book of Negroes tells that Sabinah left Ben Stratton of Eastern Shore Virginia in 1778. She probably had a surname in her head, but there was also the risk of falling into the hands of slave catchers, or owners looking to reclaim property. Thus it wouldn't be wise to use any surname that could link her with anyone from her former life.
In the Birchtown Muster of 1784, an older Sabinah Ferguson is listed, but eventually she was known as Sabinah Grant.
Canadian Census lists native born or non native nationality. My thinking is that Sabinah's kids could be safe from.slave catchers if they were Canadian born instead of American born. That's about as good an explanation as any in regards to the discrepancies in the records.