PostMortem

I think your interpretation is correct; it's older standard vs. modern standard. The real question, then, is which way is better? I think it depends on how skillfully you are able to bid with your partner in a truly natural style. If you and partner are good bidders and truly understand the structure of standard natural methods - i.e., you on the same wavelength as far as style and treatments go - and your agreements are sophisticated and nuanced (e.g., 2H followed by 3H invitational, 3H followed by 4H or the 4th suit is natural and slammish, and bidding 4H immediately is simply a choice of major suit games), then you may do better using the older standard methods. The price of this is that it can be challenging to remember and the risk of a bidding accident seems higher. I suspect the reasons why the Splinter interpretation has migrated into modern standard are that Splinter Bids (1) are easy to remember, (2) reduce the complexity of other auctions where responder has 3 or 4 card heart length, leading to fewer bidding misunderstandings, and (3) typically simplify game vs. slam decisions when holding true support. So, for players without true partnership bidding capability - for players who are not regular and frequent partners who have agreed to certain principles about bidding and formed specific agreements - the Splinter interpretation should work more effectively.