Freddy Fazbear's Pizza had a huge ton of Springlocks Outfits. These costumes were not used as the restaurant's main mascots, but rather prototypes or test versions of the new Springlock technology developed by Henry Emily.
In "The Silver Eyes" books, it is shown that Freddy Fazbear's Pizza had many Springlocks costumes. These suits were possibly created by Henry, to be used to test Springlocks. However, these costumes were not used in the main line of entertainment, indicating that they were prototypes or early versions.
In the Five Nights at Freddy's movie, we see several extra costumes in the back of the restaurant. These costumes include characters that have no direct relevance to the restaurant's theme, such as Ella, Sparky and Shadow Freddy. The presence of these suits reinforces the idea that they were developed as part of an experimental phase of Springlock technology, before being abandoned or stored.
It is also shown that Afton stole some of these suits made by Henry to use in experiments, and this may have led to the creation of Torture Freddy.
Maybe I'm stupid and maybe you all know this, but it's something I've thought about for a long time.
It's not a theory. It's a curiosity.