Maybe the more assertive "push" tells us? If you actually observe
GPs group behaviour... the top pig (dominate pig) will always nudge (push) the lesser pig out of its way like when getting to the food dish. That is at least my observation.
Besides, being assertive in the "push" using its head (also called the "Big Head" by someone) is quite a universal language of "no, I don't like it".
Now if the piggy likes it... I am sure he/she will lay all supine & let you do what ever you wanted to it.... like my lap pig Yam-Yam will get on my lap on cue to be petted (that is even without a treat, so petting is like a treat to her)). She behaves like a show pig (like in Dog show) where she'll let me do what ever to her (groom her, pet her or even trim her nails), without the big head.
Bubbles is a "Big head" kinda gal but she will jump into her pet carrier tote in the morning for a walk to get her fav. grass when I go out to collect (note: I do not harness my pig and she feels secure & stays in there just fine). Also at this point, i do not remove her from the tote yet, just let her stay in & eat the grass as I collect on the way... when we get home, I just let her jump out on her own (so no stress at all & thats why when she sees the carrier tote, she "knows").
Most important thing is to listen to your pig & let them speak to you their way... if you fight what they try to tell you... then you defeats the communication process your pig tries to tell you.