Cessna 182 pilot reported a NMAC event while taxing into position and hold. The conflict was caused by ATC utilizing misleading phraseology in their instructions.

Narrative

I was PIC in the ZZZ Cessna 182. I was listening to both Tower and our Law Enforcement Officer radio. I had moved out of the runup area and was holding short about 40 feet from the Runway hold short line. An A319 had just landed and a Pilatus had taxied up parallel to me and announced then were in sequence. Tower cleared them ahead of me; which was great as the Airbus had just landed. The Pilatus took off and about 3 minutes later Tower told me to (what I heard) 'Taxi into position and hold'. I taxied out onto the Runway; before I actually entered Runway XX I heard Tower tell another Cessna to go around and a shadow passed overhead. What Tower had actually said was 'Taxi into position at the hold line and hold'; which to the best of my knowledge in 35 years of flying I have never heard before; especially as I was already within 40 feet of the hold line and there was no one around me. It was a totally unnecessary and confusing instruction. I read back the instruction (wrongly) and Tower did not catch it. My take on this: The instruction was unnecessary and unnecessarily confusing. I was already at the hold line and there was no one else waiting such that I would have had to move for them. I should have realized that the instruction was atypical and questioned. I should have looked for landing traffic before ever moving. I should not have been trying to run two radios at the same time. I should have heard the actual instruction; not what I wanted to hear. On the other hand Tower gave a non-standard instruction that was bound to be misunderstood by a pilot sitting by himself at the hold line of a Runway waiting nearly 4 minutes to be told he was cleared to take off. 'Taxi into position and hold' is a Runway instruction. It is not to be modified for some other use such as taxi up and hold at the hold line. Fortunately it was not another A319 which flew over me; it would have flipped me upside down. When I called Tower; the Tower they must have listened to the tape as when I asked why he was asking me to move to a position I was already in using 'Runway sounding language' he agreed it was probably a bad instruction. No harm; no foul but whew!