Anyone else find fancy scoring actually hurts the oven spring?

Same thing happened to me for ages with my sourdough. I'd spend ten minutes doing fancy shallow patterns and they'd basicly vanish in the oven, just turn into faint pale lines. What I eventually learned from trial and error is that the dough only expands where the cut is deep enough to form a hinge. Anything shallow basically just sets, so now I do one proper deep cut for the actual expansion and treat the pretty stuff as decoration that stays a decoration. I also dust the decorative lines with a little flour or rice flour before baking so they still show up as contrast even though they never open. Steam is the other big factor for me. I bake in a cheap dutch oven and if I don't add a tray of water or spritz the loaf before it goes in, the crust sets too fast and even my main cut opens lopsided. When there's enough steam the whole surface is stretchy for longer and you get that dramatic peel-back on the deep cuts.

Also, blade angle matters more than I expected. Holding the lame at a shallow angle instead of straight down gave me a way better ear on my boules once I stopped slashing straight down like I was chopping vegetables. My last few loaves have actually looked like the pictures in the books, which for me was a long time coming. Congrats on getting out of brick territory, that first proper loaf is a good feeling.

I went through the pattern phase too and honestly gave up on it, but for a diferent reason than the hinge thing. Every fancy design I tried on my 78% hydration dough just muddied the crust and I lost the spring I used to get from a plain cross. Now I score one confident slash at about 45 degrees with a razor, and the ear I get from that beats anything I managed with a stencil-worthy pattern. My two loves are structure and a shiny crust, not art.

I'll push back on the hinge theory a bit. I do decorative shallow cuts all the time on my sourdough and they open plenty, so long as the dough is properly proofed. When mine were underproofed, even the deep slash barely did anything, and the shallow stuff just sat there like yours did. Once I started letting the loaves go longer before the fridge overnight, the whole pattern puffed up, fancy lines included. So I'd say the cut depth matters less than where the dough is at when it hits the oven. Worth a test: same scoring, one loaf proofed longer, and see if the shallow stuff still stays flat.

One thing I noticed with the wheat-stalk style patterns is that the dough skin matters as much as the cut itself. If my loaf has dried out at all during the final rise, the shallow lines just crack and set exactly where I drew them, but when the surface is still tacky they blur into each other and look muddy. So now I aim for that middle ground, slightly tacky but not wet, and I score straight from the fridge while the dough is cold and firm. The lines hold thier shape much better that way and the contrast after baking is acutally visible instead of being a rumor.

Cold dough changed everthing for my scoring. I do an overnight retards in the fridge, about 12 hours, and pull the loaf straight from the cold to the counter. The surface is firm enough that the blade glides instead of dragging, so even the fussy little cuts come out crisp and stay where I put them. Room temp dough always smeared on me no matter how sharp the blade was. Try scoring one straight from the fridge next bake and compare.