You raise an interesting point. The Paph Susan Booth's from the past in AQ+ are more red than your plant. The taxonomy of the praestans/glanduliferum group has changed over the years. The true praestans are more yellow in color than wilhelminae which is much darker (and smaller).
When Paph praestans is bred with roth, it will create a flower such as yours. When Paph wilhelminae is bred with roth, it creates dark flowers.
Paph praestans at one time was considered conspecific with glanduliferum as was wilhelminae, and the cross with rothschildianum was Susan Booth.
Now the praestans cross is considered Susan Booth and the wilhelminae cross is William Ambler. Unfortunately, you can't go back in time and award these plants under today's names, so there are dark colored Paph Susan Booths.
A similar conundrum exists with Phrag Grande with normal colored and dark forms. The normal forms are made with what is Phrag caudatum and the dark ones are made with what is now Phrag warszewiczianum which was formerly considered considered a variety of caudatum. The remake with the new taxonomy is Phrag Wossner Supergrande, but once again plants were awarded under the old taxonomy and there are many dark Phrag Grandes.
Your plant is strongly influenced by Paph praestans, and there is no evidence of Paph philippinense in the flower. The color, stance and conformation of the flower are entirely different from Paph Saint Swithin.