For those wondering how this issue ever became important, it might help to understand that our Canadian neighbors have been dealing with restrictions on barrel lengths, generally a mandate for barrels of 4.2" (10 centimeters) minimum to qualify in most cases.

This, of course, conflicted with most US manufacturers' long-standing practices of (nominal) 4" barrel lengths on many popular revolvers. Thus, the more standard US-production revolvers have been denied for export to Canadian dealers and customers.

So, S&W and other makers have adapted by offering slightly longer barrel lengths to remain active in the Canadian market. Over time, some of those revolvers went out to US distributors and into US customers' hands. Some frustration was created on the US side of the border because the newer revolvers may not fit correctly in holsters made for the more common 4" barrels we have seen here for many decades.

Overall, probably a very small wrinkle in human events. I do recall a time some years back when I started receiving complaints and returns of holsters ordered for a 4" S&W because the dam-thing-just-won't-fit. I had to learn to adapt because a lot of S&W revolvers produced to the Canadian standard found their way to the US market.