The embedded anime continuous effect of the any Earthbound Immortal is splitted in this trap card...
Then... Immortal creatures aren't so immortal... xD
They weren't immortal in the anime, either. They negated themselves without a Field Spell (half of them got around this with Speed World, but still), and they had zero protection from monster effects.
Every single Earthbound Immortal except Chacu Challhua and technically Aslla Piscu lost to one of these. (Either being negated by a monster, destroyed by a monster, or losing their Field Spell.)
Here instead your immortal is vulnerable also to spell/trap.
Exactly like a normal monster, the immortal don't have any embedded protection.
So, it's immortal to words only.
Again, they weren't immortal in the anime, either. Being more vulnerable here doesn't matter in regards to that, since your argument is "they're not immortal now" when they never were.
Realistically, the term "immortal" often only implies no death via natural causes such as old age or disease anyway, it's usually not used to mean "cannot be killed".
You don't have understand the point.
No one want the immortal unbeatable.
In the anime you have a reason for which you can call this creature almost immortale with a weak point (effect monster). In OCG, nope, these monsters, alone, are easily taken down over the field with a trap or a spell.