Just for interest, a brief extract i came across from the Design Code at Gravenhill:
https://www.self-build.co.uk/graven-hill-plot-passport-explained/
That line highlighted in red seems to me to be encouraging solar gain, rather than limiting it - as is more the need in well insulated houses.
AIUI the solar gain factor (ie amount of energy from sunlight that gets through to the inside) should be below 0.5 in a highly insulated house.
eg from Wikipedia
https://en.wikipedia.org/wiki/Solar_gain
However, this is not my specialism and the difference may be marginal.
Ferdinand