" Here, the lump sum just gets removed whether it will leave you in hardship or not - "
No it is illegal !
Here are the rules, Unfortunately many don't follow them as they either don't know they exist, assume that you don't know they exist so they can get away with it , or are just ****ing stupid.
If you have no income , or income below the inter professional minimum, they cannot take anything. If you have income below those shown in the regulations there are specific % that they can take. See 607 Number 1.
http://noticias.juridicas.com/base_datos/Privado/l1-2000.l3t4.html#c3s5