They do not generally reflect time passed but amount of task done.
For example, let’s say you have 100 files to configure as part of an update or installation. 99 of them are really small files that fly by, but the last one is a few gigabytes of data that needs to be configured. The bar might hang on that one really large file, then fly by the rest of the process as these files are very small and go quickly.
In this case the progress bar should show the percentage of processed data, but just using the amount of tasks or number of files is quicker and most often than not works fine
even then it would not be accurate, difference in file systems and storage medium would cause performance difference of processing many small files vs few large files. In TWRP when backing up, it would just straight up show you both progress and neither of them would advance linearly.
