So far as Current Science (Indian journal) is concerned the MSS undergo plagiarism check after finalization of the MSS. If they fail plagiarism check, they are not considered for publication.
Every Scientific journal has its roles and principles to check research and articles.. For example our journal checking it befor reviewing inorder to maintain the reviewers efforts if the checked works turns out to be stolen from others
Many journals check plagiarism immediately after the submission if the manuscript is within the scope of the journal. This is absolutely necessary to avoid the wastage of time and energy from editor, reviewer and journal office.
A number of photographs shot by me (I have proof in favour of my claim) were reproduced by two eminent Scientists in two papers in a journal in 2017 and 2018, published by Springer.
If Springer fails to detect such shameless plagiarism, and gets satisfied with a declaration that the authors have no conflict of interest, then what is the use of so many dedicated softwares?
Even the respective Institutions do not initiate any disciplinary action if such plagiarism is reported against their Scientists!