These claims exist but, as noted above, they are untrue. Claiming that the Revolution was fought over slavery is nearly as clear a case of revisionist history as claiming that the Civil War was not fought over slavery.
In the 1700s, England was hardly on an abolitionist trajectory, except insofar as the whole world was (including the southern United States) purely due to the decreasing economic viability of slavery as a whole. The world’s economy was becoming less and less dependent on the sort of unskilled manual labor that you can effectively force a slave to perform; while you can put a slave in a factory to perform more specialized labor, they’ll never perform as effectively as a free person.
At the time of the Revolution, @DrDeth is in fact correct. Most of the Founding Fathers assumed that slavery was on its way out, so rather than tackle the issue which stands in opposition to the foundational principles of the new Republic, they just ignored it, and agreed to bind the federal government in ways that would prevent it from abolishing slavery.
Two developments which they didn’t see coming occurred and entranched slavery in the Southern states:
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The invention of the Cotton Gin gave slavery a few more decades of economic viability
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The South developed antebellum culture which made slavery an integral part of the southern identify
Neither of those things had happened yet at the time of the Revolution.