No DP its not an accident as 3.14181818 is known as Fibonacci's value for pi usually written as 864/275 but as I discovered can also be written as 34.56/11 = 3.14181818181
There are at least 5 values for pi seen in the GP but will concentrate on 2 here.
22/7 = 3.142857 142857 and 864/275 3.1418181818 complement each other.
The height of the pyramid 280 x 22/7 = 880 Royal cubits or twice the base 440 Royal cubits.
Now imagine the architect decided to inscribe a circle into the base of the pyramid 440 x 22/7 = 1382.857... it dosent work and the number is not even.
To inscribe a circle into the base of the GP the architect uses 864/275 and the result is an even number 1382.4 and as you have discovered from that comes 691.2.
I know many are not coming to the party with the Indus Valley foot 13.2 inches but to keep the record straight here is how this number converts.
1382.4 Royal cubits x 25 digits = 34560 digits and divided by 16 as there are 16 digits in an Indus foot = 2160 Indus feet inscribed into the base of the Great pyramid.
We know one degree = approx. 69.12 miles x 360 degrees = 24883.2 miles and by using Fibonacci's value for pi 3.14181818 the diameter of the circle = 7920 miles or the diameter of the Earth approx.
And from the diameter of the earth 7920 miles come the number 44 by dividing it by 180.