Morgana's spellshield now only blocks just one spell?

I've just finished a game where I played Morgana, knowing the spellshields are now supposed to block only one spell, but ignoring it might have changed morg's e. And I noticed it just blocks one spell and it doesn't absorb any more damage from any other sources. So in my game there was a Sejuani going for my Tristana, I spellshielded her immediately and Sejuani engaged her with her Q, then she did the rest of her spells on her. It did block sej's Q, but her other spells went through the shield, dealing the damage and cc to her instead of my shield. The rest of my shield was just hanging there, it clearly had at least 200 hp left and it was completely useless against every magic damage coming to Tristana. After the game I went to read the exact description of Morgana's e and it says this :

Places a protective barrier around an allied champion, absorbing magical damage and disables until penetrated or the shield dissipates.

So the shield is supposed to work against any magic damage I said to myself, since it says it needs to be penetrated or needs to dissipates to not work anymore. It does not mention "Blocks damage from ONE source of damage or cc".

So I went to look at the patch (7.19) where the spellshield changes were in and it did not mention anything about Morgana's e. It only mentionned this :

AFFECTED STUFF Sivir’s E - Spell Shield, Nocturne’s W - Shroud of Darkness, Banshee’s Veil, Edge of Night

I just need to know if this is a legit change or if it might be a bugg with the spellshield changes, because I really like playing Morgana and I felt like this change was really big in that game :/

Thanks in advance for the answers.