Let's start with you explaining to me the difference between the two. What's your understanding?

They checked the car and said everything is fine. Checked the computer, ran through the gears with a 45 min test drive, said the transmission fluid looks good. If it happens again they said to bring it back.

Sounds like I need to double clutch. Could someone fill me in on this?

Don't really need to downshift to 1st at all for most common driving situations other than to make noise.
I only very rarely go to first other than at a complete stop. Maybe uphill, slowing for an acute switchback.
Don't JAM it and you'll be fine.
Rev matching has been covered here extensively as well as on Youtube.

So if you're going to a red light you just rev match till second gear and then just slow to a stop, throw it in neutral till green, and then go to first like normal?

Nah. There is truly no need to double clutch but it's a nice arrow to have in your quiver. Plenty of instructional stuff out there on the interwebz.

Because the trans has synchros, in theory you could just mash the stick into the gear you want, but the synchros are doing a lot of work to get into the low gears above 10-20mph because there is a large rpm gap. Upshifting is easy, things naturally want to slow down, but downshifting requires the synchros to accelerate parts of the tranny to higher speeds, this is a harder process. Double clutching bypasses the synchros so getting past the rpm gap is done by the clutch/engine which has way more authority than the tiny little synchros.

If you want a much more detailed description let me know. But in short- rev matching is for smoothing the relationship between the engine and car, whereas double clutching is for smoothing the relationship between the first half and second half of the transmission.

Another way to look at it, is the clutch is the synchro between the engine and drivetrain. The synchro is the clutch between input/output parts of the trans.

You were much nicer than I was. Maybe my trolldar was off. :(

Curious how the transmission is holding up...

I think the issue might be the gear selector. I've been driving the car more, but haven't had any awful crunching. Have had some trouble changing into first so I'm monitoring it.

Right now everything seems okay.

Change the transmisson fluid to something like motul gear 300 when you have problem next time.

Our transmission is build with tighter tolerance & it can be weird sometimes with stock fluid.