What you do not realize is that heating the fitting with a propane torch will ruin the spring that holds the check ball. The fitting now no longer seals and grease can leak back out, contaminants can go in.
Carefully heating the fitting with a heat gun till the grease starts flowing, without overheating might save the spring.
I have encountered my share of pressed in fittings and dislike them. I have had to tap new threads and replace them with threaded grease nipples many times.
2006 GMC Sierra 4.3l, NV3500,G80 , Mobil 1 5W30, Dexcool.
1987 BMW R80 - sold
2015 Honda CBR300R
Staying out of the right lane a lot.