Caveat Lecter wrote:
"To what extent does this (aperture) apply to HF?"

To the fullest extent of the concept. See the 3rd edition of Kraus`
"Antennas", Section 2-11, The Radio Communications Link, beginning on
page 336.

Radio antennas scale to wavelength. Microwave antennas may be
impracticably large when scaled to longer wavelengths, but if built work
exactly like their higher frequency models.

Best regards, Richard Harrison, KB5WZI