Not only is it ok, it´s highly recommended. Those slopes accumulate debrish in huge quantities and in the deepest parts anaerobic conditions can appear which will allow for certain types of bacteria to flourish which produce very toxic compounds. If those compounds are released they could potentially wipe out your animals.
Get rid of the slope. If you use any substrate it should be a layer no thicker than an inch to prevent anaerobiotic conditions and it should be either very fine sand, or large enough that it could never be swallowed.
Another reason why the slope is unneccesary is that the land area itself is unnecessary. Healthy, well adjusted H.orientalis behave 100% aquatic if conditions are adequate. A piece of floating cork bark is more than sufficient for them to haul onto if they need to. Elaborate land areas are a waste of valuable volume.
All the newts need is 10 gallons or more of water, ridiculous amounts of plants occupying the water column and reaching the surface and a piece of cork bark just in case. That´s it.