If i change smelting time from mod settings to 0.1 i see 6.4s crafting time from compressed iron ore to compressed iron plates.
You might have changed the smelting result multiplier, which is 1 by default. That is a self-balancing ratio with an exponentially scaling formula, and is by design. The thought behind it is, if you make 2 ores yield only 1 plate that is negative productivity and i wanted to reward that by making the crafting time even less than just half. And on the other side if you get more than 2 plates from 1 ore it is cheating and one should get more time cost.
In prototypes\functions.lua line 16:
simpleCompress.CompressedSmeltCost = simpleCompress.DefaultSmeltCost *
simpleCompress.CompressAmount * math.pow(simpleCompress.SmeltRatio, 3) *
simpleCompress.SmeltingTime
If you change it to:
simpleCompress.CompressedSmeltCost = simpleCompress.DefaultSmeltCost
.. it should then work as you expect and more cheaty. To do that you should probably extract the mod zip into a folder inside mods\ and make change there.
I would still suggest doing actual cheating with other mods, such as some very powerful productivity modules or extra levels of quality etc. Smelting result is better kept at 1.