Yes they were Christians by their definitions.
And wrong on their strict way of raising those children.
Some will take it ok and some will rebel. some are too meek to do either.
They carried it to the extreme. Christians come in all sizes and colors... strict and hells bells...
Just being one does not make us perfect.
I’ve heard the adult daughters are “rebellious”, in that, they wear pants now as adults. Which was not allowed for them growing up. Many have their own families now and seem not to be as strict as their parents were, in raising their own children.
I also heard a few have joined other Christian denominations, and left the strict Independent Baptist denomination they were raised in.
Just saying, many of the adult children are making their own decisions about their lives.