Just had a look at Erik’s prime reference point which is the Grand Slam wiki page and shockingly it doesn’t reference the Silloth Family Foursomes. But what it does say in the very first line is;
“The Grand Slam in professional golf is winning all of golf's major championships in the same calendar year.”
That’s pretty definitive on what a Grand Slam is. You’ll note it’s not referred to as the calendar year Grand Slam. Then it goes on to say;
“Other variations include the Career Grand Slam, winning all of the major tournaments within a player's career, or the non-calendar year Grand Slam, also known as the Tiger Slam, holding all major titles at the same time although not in the same year.”
So Erik’s source firstly defines what a Grand Slam is, and then secondly, that Tiger’s achievement doesn’t meet that definition.
In case Erik think that is semantics, here’s another quote from Erik’s prime source;
“Only Bobby Jones has ever completed a Grand Slam. No man has ever achieved a modern era Grand Slam.”
Of course the wiki page hasn’t been updated since 29th June 2019 and as we all now know the English language moves ever forward
Niall