Why While Editing a Next it adds p tag inside the block

While Editing a Text Block it adds p tag inside the block by adding this the text block size as been increasing because of p default margins but in normal ckeditor behaviour its not happening like this and also even in grapesjs newsletter example this is not happens what is correct configuration for that

https://codepen.io/darrenbawag/pen/JjWBLrp

this is on preview