*This is related to physical file size of a MDF or LDF file not internal allocation.

One of our user asked that the ldf file is not changing, on checking the last modified date time, user was asking this.

Its a good question, the we have to educate to user that the mdf and ldf file gets modified at the time the file  grow/shrink this could be happen due to:

during auto increment set to ON, the depending upon increment with value if file gets reach to max it will grow the file with incremented value.

during manual /auto shrink(not recommended) the file will be shrink.

if we make manual changes in the file(grow/shrink) could also cause file change.

In short : data and log file will not change with dml (insert/update/delete) command but if the file has to grow/shrink which indirectly depends upon dml(when file reach its max growth).