Yeah I agree there is variabilty in zibethinus.
I am also unsure how many cultuvar that we call zibethinus that actually could be hybrids with, kutejensis, lowianus, graveolens, dulcis and oxleyanus.
According to Anthon Lamb, Wild durio zibehinus in Borneo has very white flesh small spikes and is quite bitter. It’s in A guide to wild fruits of Borneo.
I’v got a zibethinus x dulcis and know that there are zibethinus x graveolens and zibethinus x kutejensis.
Havent heard of oxleyanus hybrids but suspetc it is possible.
Durian Suluk is a graveolens hybrid i think and its a F3 hybrid i think. So it’s been through 3 crossings if I am not wrong.
There are lowianus and zibethinus hybrids, poscii on the forum knows a tree and I have a photo somewhere.
How many seeds of the fruit did you plant?
Did all grow multiple roots?
I have seen zibethinus grow multiple roots so can happen, it’s usually when the seed is not very big or unhealthy.
It could be lowianus. Lowianus is really bitter and less sweet, but I have only tried it once in Thailand.
There are diversity in lowianus fruits too.
I would look at the flower for clear ID.
Strong durian having great growth during winter!