Digital recording and digital editing are incredibly easy and cheap compared to the ’old way’. This is why it is so popular. Sure you get the usual spin about ’sound quality’ but cheap and easy are the cornerstone benefits. Producing a good quality (quit your quibbling, it’s a relative term!) digital recording is easy, so easy in fact the only thing easier is producing a bad digital recording! Digital editing is so cheap that except for your time it’s basically free. This is what is going on with so many of the reissues. Find some version of the analog originals hopefully the multi-track masters not the two-track ’masters’, digitize it then re-mix, edit, EQ re-order to your hearts content. Many believe that a simple A/D -- D/A guarantees a superior product and $1 bins are full of those. Fortunately there also exists a group who actually do what onhwy61 thinks ’most’ of them do and get as close to the original multi-tracks as possible and re-master them. Lots of objective fixes like channel balance, bandwidth roll-off corrections etc. Many of the changes are of the subjective or ’taste’ variety. Bring the drums and bass up a little during a guitar solo or position backup vocals around the vocalist instead of off to one side. Always the hope for the buyer is greater clarity and range, less hiss and noise more ’immediacy’ etc., some do a great job others make you wonder what they were thinking. Long winded answer to you question I know so to summarize; yes, the terms get thrown around like confetti so the meaning is kind of fluid. Information on how each was done is out there for the significant reissues with lots of clues as to the potential for success in each case. How successful they have been is up to your own ears. Check reviewers you trust but be aware of each’s biases.
I have tried in several forums to get record buyers to talk about their experience with new re-issues focused on the physical record. I have owned or heard many super audiophile reissues that had incredible sound but very quickly (1 play sometimes) develop clicks or pops that are startling in an otherwise black soundscape. Some look so good you just know the sound will be a knock out then you learn the groves sound like a chain hanging off the back of a pickup truck on a gravel road. Any takers here?