We've noticed a shift in how files are opened in the latest versions of InDesign, leading to instances where file locks aren't generated. Consequently, if one user has a file open in InDesign, another user opening the same file may not receive a warning that it's in read-only mode.
This behavior has been observed for Indesign 2023 (since version 18). Adobe has resolved the issue in Indesign 2024 (version 19.1 onwards).