Many jurisdictions have enhanced disclosure requirements (over and above those which comprise the substantial shareholder disclosure regime) which apply to shareholders generally who hold or deal in the securities of a bidder or a target in an offer period.
Often these thresholds can be much lower than the thresholds for disclosing substantial shareholdings.
The reporting obligations apply because you hold securities in an affected target or bidder. It doesnโt matter if you are involved in the bid.