5 Ton AC or 4 Ton AC

Hi Guys

I have an AC where the Evaporator coils are leaking. I have American Home Shield. AHS technician is good i feel. He said coils have to be replaced along with the Pan. I currently have a 5 Ton coil with a 4 Ton AC. I asked him what coil would he replace. HE said he would put in a 4 Ton coil. AHS has given a cash out option.

My only concern is that why isn't AHS guy putting in a 5 Ton coil. I asked him. He said he might not find a 5 ton coil or it might not fit. In that case, he will have to replace the whole system. I have a few questions for you

1) Can a guy still find a 5 Ton coil? Mine is a R22 system.
2) Will the 5 Ton coil be bigger than what i have today and might not fit
3) When he says he will replace the whole system, what does that mean? Does it mean he will replace the whole AC?

I am trying to find out if i should get like for like replacement i.e. since I have 5 ton coil , they should replace with a 5 ton coil and not a 4 ton coil. I am basically trying to get more money from AHS. Trying to figure out if this would work or not.

Thanks and please advise