Former Client Threatening Legal Action Over A Generic Notion Template I Built For My Portfolio. No Nda Was Ever Signed. Is This A Legitimate Threat?

Location: Oregon

I'm a freelancer. I had a contract on Upwork that ended badly and now my former client is threatening legal action. Looking for perspective on whether this holds any water.

Background:

I was hired as a VA but over time my responsibilities grew significantly beyond my original scope. I eventually proposed ending the current contract and starting a new one with a more appropriate title and better compensation to reflect the actual work I was doing. The client had also verbally promised to transition me into a higher role with better compensation within a week or two. After two weeks passed with no update, I followed up asking about it. Before that could happen, the client terminated the contract abruptly over a time zone miscommunication related to US daylight saving time. He also did not pay me for my last shift.

After the contract ended he gave me a 5-star review on Upwork.

The issue:

During the contract I built a Notion-based SOP and knowledge base as part of my role. The work involved permit research using publicly available government data from municipal websites. After the contract ended I created a completely generic version of this as a portfolio piece on Upwork. No client name, no company data, no proprietary links, nothing specific to the client. I also added a disclaimer stating it contains no client materials and is sourced from publicly available information only.

The client is now claiming breach of contract, saying his attorney is aware, and implying legal action over this portfolio piece.

To give context on what he believes is proprietary, here is his exact message:

'The Permit research is our idea, you knew nothing about this until you worked for us. THIS IS BREACH OF CONTRACT. THIS IS ALL PRIVATE AND PRIVILEGED INFORMATION THAT BELONGS TO US. You cannot use it any shape or form'

He is claiming ownership over the concept of permit research using public government data. No NDA was signed, no confidentiality agreement existed, and the portfolio piece contains zero client data.

I'm not even new to Research as well, since I've done projects involving B2B Lead Generation and Quality Assurance (ops work) before this gig and during.

Key facts:

• No NDA was ever signed
• No written confidentiality clause beyond the standard Upwork contract
• The template contains zero actual client data
• The research was based on publicly available municipal government websites
• He left a 5-star review after the contract ended
• The threat came after I proposed better compensation and a contract restructure

Is this a legitimate threat or retaliation and intimidation? What would actually need to exist for a confidentiality breach claim to hold up here?