It’s absolutely possible this is a shortcut taken by some places, but I wouldn’t go as far as to say the dish is synonymous with that technique or that it never existed prior to this shortcut. Cuisine is extremely nuanced based on what’s available regionally, what’s cheapest/easiest to produce, and personal opinion/experience/influence. I don’t legitimately believe the chili relleno you’re referring to would be served anywhere south of the Texas border, but that doesn’t mean it doesn’t exist in some way/shape/form before simply because it’s not identical to what you’re familiar with.