I'm developing the integration of TerraFirmaCraft glassworking via Create machinery for my modpack, and it seems the curving press can't be integrated into a sequenced assembly.
This is the KubeJS script for this recipe:

event.recipes.create.sequenced_assembly([
Item.of('butcher:jar', 1)
], 'tfc:silica_glass_batch', [ // input
event.recipes.vintageimprovements.turning('tfc:silica_glass_batch', 'tfc:silica_glass_batch'),
event.recipes.create.pressing('tfc:silica_glass_batch', 'tfc:silica_glass_batch'),
event.recipes.vintageimprovements.curving('tfc:silica_glass_batch', 'tfc:silica_glass_batch').head('vintageimprovements:convex_curving_head'),
event.recipes.create.cutting('tfc:silica_glass_batch', 'tfc:silica_glass_batch')
]).transitionalItem('tfc:silica_glass_batch').loops(1)

But it gets stuck in the curving step. It even creates the proper tag into the object, as seen here:

But the curving press just doesn't process it. I'm not sure if my script is somehow wrong or if the curving press just isn't supposed to be used in sequenced assembly.

I was about to raise an issue about this but I will add to this instead. Maybe it can also help you ?

I have been experimenting with curving press in assembly line for TFC recipes for the Gravitas² modpack and I was able to successfully create one for armor smithing which involved the curving press and the helve hammer over a TFC anvil. And if I just make one recipe that has a particular starting item (wrought iron plate => wrought iron chestplate for example), it works.

But the goal was that each armor piece recipe would begin with a curving press step with a different head as a way to distinguish which sequence to start on the same starting plate item. 4 armor pieces, 4 curving heads, it was meant to be. But as soon as I add a second sequence with a different curving head (e.g. wrought plate => wrought helmet with the concave head) then both recipes become non-functional (the curving head does nothing) despite both being properly registered in JEI.

So my conclusion is that while the curving step looks different on account of the different heads, the game cannot actually tell the difference and thus does nothing. It is as if I created 2 sequenced assembly recipe starting with a regular press hit on the same plate.