It’s possible that some of the letters have been enhanced in order to ensure good definition when stamped in silver on grey leather, but I doubt very much that Fulgur have designed new letters. In any case, you could always email them and ask.
I have a 1954 stele with some letters of the Sacred Alphabet. I’ve never checked them against the examples in The Book of Pleasure, but it’s always possible that Spare came up with some new letters in his last few years. Given that the letters express sensation as graphic, you’d expect some flow and change across the years.
No, they are not only enhanced. First of all the lines of sacred letters in Logomachy consists of five letters per line, and the combinations of letters are entirely different from the first edition. The double knot letter in the first row on the cover has been rotated for instance. But I don’t know if the letters on the cover are taken from the Logomachy in the Collector’s edition or from somewhere else. If you don’t know the answer, I’ll follow your advice and write a letter to Fulgur. Thanks.