I don’t accept that “rūpa” means the physical body, much less matter. Please see here for my reasons as to why it likely means “image” or “appearance”: Meaning of rūpa and its implications - Q & A - Discuss & Discover (suttacentral.net)
What you are aware of in the jhānā is an image (rūpa). This is what is transcended in the formless attainments (along will the 5 senses). For example, when working with the earth kasiṇa one’s entire perceptual field will be filled with one perception, one image (rūpa). This is what is then dropped to enter the formless. The perception of the 5 senses, which includes the body, is dropped to even enter the 1st jhāna. The jhānā are of one perception and one perception only, which is why you can’t be aware of the physical body in them and so why body here does not mean the physical body. To be aware of the physical body whilst in any of the jhānā would be a hindrance, since multiple perceptions (saññāmanasikārā)are a hindrance to the attainment.