I'm just saying that's how it's supposed to work. You can think of the synchros 2 different ways. The synchro is supposed to block you out of gear until the gears are spinning the same speed. At the same time, the synchro is like it's own little clutch. When you're pushing against the synchro it's trying to spin the input shaft up or down to match the output. Once they match it lets you in.

In real life, you can push hard enough against the synchro, and it will let you engage the gears before their revs are perfectly matched. That's when it grinds. As the synchro wears out, gets weaker, you don't have to push real hard to push thru & grind. I'm sure with the diameter & surface area of the cones, a synchro can be designed stronger or weaker. They wear out, too. That's why they don't all act exactly alike.

If you're in gear and accelerating, the forces on the gearset keep you from shifting out of that gear. That should still be the same without synchros, like in reverse.

When you shift normally, you disengage the clutch so the input shaft is coasting. When your slave went out, you couldn't disengage your clutch. So when you try to shift, the synchro isn't strong enough to force your engine to match revs. If you push against the synchro & wait until IT LETS YOU IN, it won't grind. So if it grinds, that just means you didn't really match revs accurately.