I personally prefer a mix of water-based and Crisco, but I have found that water, j-lube or oil based lubes are all safe to use on my toys. The word on silicone based lubes is that I must advise caution and perhaps to avoid using them altogether.
A few other manufacturers of silicone toys have not recommended their use. I have not had any short-term adverse effects on my own toys by using silicone lube, nor have I yet to receive negative feedback from fellow players. It does raise the question however of what the effects might be over the long haul. I personally don’t prefer silicone lubes simply because I cannot ever get it all off once play is over. There is always some lube left on the toys to attract dirt.
But, there are literally thousands of different types of silicone, so maybe those manufacturers are using one that reacts adversely to silicone based lube. I did read on one site that they used a microwave to “cure” their product, which indicates to me they are using a silicone completely foreign to me. No heat is used in my production process. Another plausible reason would be that they know how well silicone adheres to itself in casting, but this only applies to silicone in the uncured state, not in the state you find the toy or lube. As a result, this could just be a precautionary measure on their part.