speed variation between glossy and matte? (Ilford multigrade FB)

Is it just my imagination or is there really some kind of a difference of speed between Ilford MG IV FB Matt and Glossy?

I started with a contact print of a 4x5 negative.
From that understood what I needed to dodge/burn and roughly what my exposure should be with larger paper, first 8x10 then 11x14. The contact print and the 8x10's were initially RC paper. I noted their times, and fstops. Each time I increase I know roughly to increase one stop, two, one and a half, whatever. First time is guesswork but usually it pays off. I went up to 11x14 in Fiber Matt. I find that the RC paper is a little faster than the Fiber Matt paper. Not much but somewhat, like perhaps a quarter stop. I exposed and developed the 11x14, and sure enough it is right in there, so I make another with a slight variation to have one for bleach/split toning and one just for selenium archival toning. Then, my long awaited 16x20 easel comes to me by FedEx and I went to make my first print last night.

I did the same math I have done before for the first exposure. It came out about a stop or a stop and a half lighter than what I calculated it should. The difference here is I cannot find 16x20 in Matt my preferred paper, only in Glossy. So what I'm saying is the Glossy is possibly slower than the Matt in Ilford Multigrade FB paper.

What I want to know is has anyone else noticed this?