Is this safe?

[Peanutthepigleto]

I know that you should never force a guinea pig to lie on it's back. Yesterday my relative came over picked up my guinea pig and in his hand flipped him over gently and while holding him rubbed his stomach, and my piggy seemed to like it. Also lately both of my piggies started making a chewing noise, and I didn't feed them vegetables. I just wanted to know if this is normal in other piggies.

 

[alice daisy and popcorn pig]

I'm not sure about them being on there backs as it makes most piggies scared as they think predators will get them but making eating noises has always been normal with all the piggies i have owned (8). So i have never worried about this.
hope this helped