Absence of evidence is not evidence of absence. Show me some high level games where CE spam gets stomped if you think it's non-viable. I'd argue the reason you don't see it that often is because 'that's not how you play the game' rather than ineffectiveness.
I'm not familiar with OKW and thought SP were a tad more expensive. Do you think sturm pios are more cost effective than volksgren?
I didn't push CE vs conscripts.
A 5% difference in reinforce cost and 7.5% difference in pop is kinda splitting hairs when CE have a 10% increase in RA.
I compared CE to conscripts because they're in the same army. There's a wide variation in mainlines, but they're generally agreed to be balanced against each other. If CE are on par with conscripts it follows they'll be on par with the other mainlines despite more varied stats.
3 CE will beat two of any mainline infantry except for charging rifleman in open cover, and max range infantry sections if you want to go down this road, but your interest seems to be muddying the waters rather than taking a critical look at things.
I've never seen a CE spam build used by a high level player even as a joke. You would think this wouldn't be for any gentlemanly reasons as cheese strats have a habit of making their way onto youtube regardless of perceived fairness.
Why don't you try a CE spam strat then and show us a replay of it in action? Regardless of any minute 0 efficiency compared to conscripts by virtue of using the same weapon and having better RA, you should know CE receive no RA buffs with vet and only marginal accuracy and cooldown bonuses. By the time any enemy infantry gets vetted, much less light vehicles hit the field, CE would be basically hopeless; a build centered around them would fall apart almost instantly.
SPios are more or less the same way to an extreme; they have great DPS and even get an AT package. But in the end they scale worse than Volksgrens and bleed harder to boot.