I think the more common terminology is "jump-shift", jump-reverse would be reserved for auctions like 1♣-1♠-3♦.
reverse = non-jump bid in new suit, suits bid out of economical order so that preference would require partner to bid to higher level
jump shift = jump in new suit, where just bidding new suit cheaply is not a reverse.
jump reverse = jump in suit where just bidding it cheaply would be a reverse
Again, I think "unplayable" is an overstatement. However, I do believe that the vast majority of intermediate players claiming that the jump shift is only a one-round force only do so out of ignorance rather than because they are knowingly using some special treatment with agreement from their partner. J.S = game force should be assumed, & absolutely standard, without some very special agreements.
But a regular partnership with special agreements can do some interesting things with j.s. = one round force ...
There's an argument for not ever jump raising partner's jump shift suit, and not treating the single raise as unambiguously being a slam try -- such suits occasionally turn out to be fragments (3 cds) rather than actual 4 cd suits. Since the jump shift is the only forcing call by opener in std, with some one suiters (3-3-0-7?) opener might be manufacturing a jump shift suit in order to create a force. Bidding 3♠ only would leave room for opener to bid 4♥ with such a hand.
Since one is always going to game after a std jump shift, there is less need for a negative than after a reverse, which would stop in a partial with reasonably large frequency. One can cover slam/not slam by refusing to cooperate with cue-bids subsequently. Opener shouldn't drive beyond game w/o responder cooperation, since the jump shift already shows substantial values, and has limited the hand to a reasonably small 19-22 range.