So I found your article. It says its based on an Axios article:

https://www.axios.com/manchin-outlines-bbb-deal-requirements-723696b5-c602-42ef-907c-fcf08bab96f6.html

"Manchin’s private comments... are a clear indication he’s serious.... for a smaller version of President Biden's $3.5 trillion proposal, people familiar with the matter tell Axios."

So, the source is someone who claims to have heard him.

"....his office is reviewing new legislative proposals. That may be an indication he's serious..."

Again, not a comment from Manchin, rather people guessing his intentions.

If he votes for $1 Trillion tax hike, he is 100% an asshoe, but, he hasn't, nor has he said he will. Let's not jump on the rumor bandwagon. Journalists are not known for telling the truth these days