Actually, a lot of the bl webtoons and mangas we read are novel adaptations. Not only bl but for many genres as well. Lots of people are only discovering it now because we are crazy for spoilers and since most novels that are adapted to webtoons are finished, many readers want to read the novel to find out how things progressed or ended.
The novels are usually more detailed, vivid and thrilling to read but My preference is I like to read the comics first because if it doesn't live up to the high expectations the novel gave me, it would be a much softer blow on my frustration with how things are portrayed HAHAHAHAH
ε=ε=(ノ≧∇≦)ノ
I've read too much novels that were later adapted and lots of my favorite scenes weren't illustrated. The heartbreak and let down of my expectations are bad.
I don't think this is a new thing. I wasn't aware before but I'm pretty sure many Manhwas are from novels, not all though. Not all of the novel is being adapted, sometimes they leave out some part of it. You'll only know if your read the novel. Adaptations are basically taking text work and making it into art or comic. Whether you read the novel first or not is fine, you're probably confused because you're getting spoiled and I know how that feels. It's okay if you don't read the novel and just read the manhwa, I do that too. But you can read the novel if you want to know more of the story and have better understanding, ask for the novel link in the comments and I'm sure there's people who will provide it to you!
My answers may not be accurate and I hope someone will correct me if I'm wrong but I hope this will help you ^^

Maybe i’m clueless or haven’t been paying attention.Ive been reading yaoi/bl for 6 years now.I just noticed a few days ago tht some of these magas are from novels…is this a new thing?Are all these stories from novels or just some?Are the adaptations or inspired?Should i read them first before the manga?Idk but im very confused because i keep seeing novel in the comments of every new manga i read…So please help me understand what’s going on?