I’m a firm believer that directions are there for a reason, in life and in sewing! If a sign says road closed you won’t drive down it and if a pattern says use a facing, you do right?
For me this is a huge grey area.
When I was making my Betty dress I lined it because my fabric was a bit sheer, but I thought about whether to do it for days leading up to it. Would Sew Over It still accept my dress into the competition for sewalongers even though I didn’t completely sewalong? When I made my first Elisalex I didn’t line and instead made a facing because I had nothing suitable to line with. I worried that it wouldn’t look right and would lay funny but I was wrong. In both cases, everything worked out.
In the end, the garment is for you so facing, lining, bias binding, etc, are a matter of your personal preference. The directions may be based on the creators personal preference so unless the directions explicitly say, “Use the facings provided instead of fulling lining because a lining will not lay nicely”, then I say go for what feels right for you!