It's an engine change. Whether you think it's a substantial nerf or a "huh, that's different" depends on the character and the opinions of individual players that play that character. I'd say the biggest technique we got out of it before the patch was the ability to run to the end of a platform or to a ledge and perform a certain side special attack in order to fall off the ledge lightly rather than run off. The Side B in question would get cancelled as the character falls, and at the ledge, they would grab it. Bowser, Ness, Samus, and Mii Gunner could perform this, allowing for a slower-but-easier to perform ledge trump method. Other than that, it wasn't a core technique to their gameplay. But again, that's just my opinion.
Indeed, I performed the same test, but continued until the Ftilt did 10% damage one more time, and it did on the 14th strike (142 to 152%). 142 divided by 13 is a number I rounded to 10.92. I don't think Lucina mains care that the actual buff is 0.95% damage instead of 1.00, but I did want it clarified that it isn't 1.00.