“It is often stated that the Union Flag should only be described as the Union Jack when flown in the bows of a warship, but this is a relatively recent idea. From early in its life the Admiralty itself frequently referred to the flag as the Union Jack, whatever its use, and in 1902 an Admiralty Circular announced that Their Lordships had decided that either name could be used officially. Such use was given Parliamentary approval in 1908 when it was stated that “the Union Jack should be regarded as the National flag”.”

Winston Churchill who apart from Prime Minister had been First Lord of the Admiralty universally called it the Union Jack in his speeches regardless of context.

So the idea that it should only be called the union jack when flown at sea is a ‘relatively recent idea’ which you are promulgating in this website. Perhaps you can update your website instead of continuing to promote this urban myth about the name of the national flag.