I understand why they did this, otherwise a single missing source block in the ocean could ruin the growth. However this is still an oversight.
In my opinion, it should only be able to grow into flowing water (and turn it into a sourceblock) if the block above is also water (source or flowing). This would make it the best of both worlds, the kelp mechanic to create functional bubble columns can stay and farms will not be ruined.
From a logical perspective, this also makes the most sense in my opinion as it would still allow kelps to grow normally in the ocean while preventing weird behaviour like this:
L0laapk3
I understand why they did this, otherwise a single missing source block in the ocean could ruin the growth. However this is still an oversight.
In my opinion, it should only be able to grow into flowing water (and turn it into a sourceblock) if the block above is also water (source or flowing). This would make it the best of both worlds, the kelp mechanic to create functional bubble columns can stay and farms will not be ruined.
From a logical perspective, this also makes the most sense in my opinion as it would still allow kelps to grow normally in the ocean while preventing weird behaviour like this: