I've been playing a long time as well (1998), and at that time...stocks WERE halted on Saturdays, but we could not short in those days either. We also could only own 10K shares of stock in those days.
Many players would log on, find out how a movie did and either keep their stocks if the movie opened well... or sold them off if it did not.
Even though I have the money, I don't know that I'll buy a short & long of a stock when it opens and then sell off whichever is the 'wrong' choice... of course, there's still the commish involved to do that as well.
While I'm not sure 'why' HSX is moving to a Saturday halt, with the increase in shares to 100K this may have some additional reasons behind it too. Just as you, I've seen lots of changes over the years with the game, and playing openers is still one of the main reasons I'm here.. it's just a matter of seeing how good I can guess for what I'm holding.
There's also nothing to stop you from choosing to play either short or long an opener, or not playing one at all, or buying BOTH a long and short of it... it all depends on how YOU want to use the game for playing. Personally, I will probably still only buy a short or long when a movie opens, there's no fun in knowing all the answers to ANY game when you play it.
For whatever reason HSX is making changes to continue to bring players to the site, some of these changes may be good or bad...but unless they try different things... we'll never know.