Yes it was traditionally a pro health fad food - and this is precisely one the reasons Wendy’s is marketing it. That and it still has a little panache as being more “upscale” than iceberg.
In the 00sKFC tried to market their chicken as a pro health Atkins type food with none other than Jason Alexander. That one was so bad that even the fucking ad industry criticized it. Marketing the unhealthiest of fast food as somewhat healthy is not a new thing.
KFC was considered healthy by the uneducated long before that. Growing up in the late 80s, early 90s, I remember my family and my friends' families treating KFC as the healthy fast food option.
It really wasn't until the Double Down era that the absurdity of KFC was apparent to everyone.