That is because the latter is a free app, which recently added bloatware and ads, before releasing a pro version to remove the ads.
Previous buyers won’t see any ads though, as long as you have the unlocker app installed. Also, previous buyers can use the new Material Design version of the app (separate download), with the same old unlocker app.
New users can also remove ads and unlock the Material Design as well, by purchasing the Unlocker for $1.99 (Rs 112 in India).
You need version 1.7.0 to use it for free. All previous versions of the file explorer app, have a two-week trial period after which you can’t use it.