Yes, formal incorporation of Granby occurred in 1786—separating it from Simsbury. However, Granby was a named area earlier though it was akin to Tarriffville and Weatogue "neighborhoods" or areas under Simsbury governance.
As to your question. Yes, Thomas, the father, could not have been buried in Granby as presently showing on his profile.
However, it's unlikely that any burial source of other persons presently showing with burials in "Granby Street Cemetery" or "Granby Cemetery" before at least 1706 are bogus as to the place of burial—unless Granby Street Cemetery was not in Granby but on a road once and later called Granby St. The basis of my argument hinges on the a source I previously included in this discussion along with two old sources I found at the Granby Library yesterday.
To clarify things for persons unaware of our area, knowing three things is useful to understanding the source quotations that follow.
1. There was only one Granby before 1858.
2. East Granby separated from Granby in 1858.
3. West Granby and North Granby have long referred to parts of the town of Granby.
SOURCE ONE: “Granby: Early History”, Compiled by Eva Dewey – (a narrative paper, not formally published.) — All-Caps below added for emphasis.
“It is believed the first house stood at the Falls, now in EAST GRANBY, and a little less than a mile north of the village of the town of Tariffville. This was occupied by Sgt. John Griffin of Simsbury (or https://www.wikitree.com/wiki/Griffin-197 ) as early as 1664, and he was probably the first settler. He was given the first Indian deed. The next settlers located at salmon Brook in Granby proper, and the first house stood near the present home of Paul Avery which is next to the South Congregational Parish House.”
“Daniel Hayes of Indian fame lived about 1720 in a house that stood across from the Firehouse on Salmon Brook Street, South. The lilac bushes and the lemon lilies that were by that home may still be seen….
“Frequent attacks and murderous outbreaks, kept the early settlers in a perpetual state of alarm. Most of their energy was needed for personal safety rather than civic improvements.
“One most noteworthy event was the capture of Daniel Hayes by the Indians, who was then twenty-two or twenty-three, when he was on his way to the pasture in search of his horse. He was carried off to Canada and after several years as a prisoner was sold to a Frenchman who permitted him to buy his freedom. He returned after an absence of seven years,...
“Settlement and population was very slow. AS LATER AS 1709. there were only eleven families. In 1736, two Ecclesiastical Societies were established. All public measures prior to 1786 required the approval of the Town of Simsbury...
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SOURCE TWO: “The Heritage of Granby 1786: Its Founding and History”
“…The area west of Windsor, sometimes called by its Indian name of Massaco, was incorporated in 1670 as the Town of Simsbury, and within the town several settlements sprang up. [Note: Simsbury was settled in 1640 before in was incorporated or separate from Windsor.]
“Settlers gradually moved out from the center of Simsbury and established their homes — first along Salmon Brook Street in Granby center and then in the area around Simsbury Road in West Granby, along North Granby Road (on the road to Granville, Mass.) and in the Turkey Hill section of East Granby.
“The church was the ruling factor in the towns — not only for religion, but for government and education as well. A central meetinghouse had been erected in Simsbury for which all the people in the town were taxed. Families living on the outskirts were unable to cover the distance to use the meeting house built with their money, and feeling ran high over this state of affairs. So in 1736, the General Assembly divided the areas so that meeting houses were built near to the largest groups of people. Salmon Brook in Granby was one such area, or Ecclesiastical Society, and Turkey Hills in East Granby was another. These Societies were responsible to Simsbury until the town of Granby was incorporated in 1786.
“SETTLEMENT of the TURKEY HILLS section commenced ABOUT 1700….”