One of the ways that copyleft works is by mandating that users of modified versions of GPL'd code are required to share their modifications with anyone who asks.
No, distributors of modified versions are required to share their source code (and possibly only with those downstream).
What if, going forward, users of GPL'd code are required to post the way that their tools are being used?
If this applied only to corporate users, it might be reasonable, though for very specialised software it could reveal information that they reasonably want to keep secret (e.g. that they're working on a new product line).
If this applied to individuals it would be an unacceptable privacy violation.
Re: A requirement to post FLOSS software usage?
No, distributors of modified versions are required to share their source code (and possibly only with those downstream).
If this applied only to corporate users, it might be reasonable, though for very specialised software it could reveal information that they reasonably want to keep secret (e.g. that they're working on a new product line).
If this applied to individuals it would be an unacceptable privacy violation.