The old flag of the Republic of South Africa was not a Boer flag as it was a flag which came about as a compromise flag between the 3 main White ethnic groups of South Africa in 1927. An acrimonious debate prior to the adoption of the flag almost caused the break up of the State & Natal considered a motion to secede from the union. The orange / white & blue colour scheme was adopted due to the widespread belief that it was the first flag ever hoisted at the Cape & was no longer being used in 1927 by any other nation-state thus was considered to be a flag which could not be confused with the flag of another nation-state. This flag was later adopted by the later Republic of South Africa as the RSA never adopted its own flag. Though there was a strong movement to abandon the flag & a plan to replace it was initiated in the 1960s prior to the assassination of Prime Minister Verwoerd but was itself abandoned upon the ascension of Vorster to power.
This flag made on odd come back in recent years & was seen at Bok van Blerk concerts despite the fact that the Orange Free State Flag [ an actual Boer flag ] was seen in the De la Rey video. A lot of Boer descendents appear to be oblivious to the true nature of the flag. This was the flag of a macro State in which the general White population were granted nominal voting rights but one wherein the actual Boer people were outnumbered within the White population.