As I said, having been there on more than one occasion, I cannot agree with you. When HM rode she gave and received the salute once only.
When the tune known as the Royal Salute (National Anthem) is played, you are expected to stand, whether that is in the theatre or anywhere else.
Royal Insight > Out and About > Trooping the Colour
We can go on and on about this and other ceremonies that we have personal knowledge of, I am not going to convince you and you are not going to convince me. As with almost all military parades, the reviewing officer only
takes the salute once, although there are other salutes within this parade, all called royal salutes (except saluting the colour).
Edited to add the following
I, my husband, son's and all the links I posted all got it wrong, HM takes umpteen Royal Salutes and the first is just one of many, which is obviously why only the one is mentioned.
The reviewing officer on parades also takes more than one salute and the MOD has also got it wrong.
They clearly all need writing to, so that they are able to correct these universal & horrific mistakes!