Custard Pineapple Buns - More Water Roux Bread - Tangzhong

I tried the tangzhong method again, the water roux.
I can't say I followed the recipe exactly, but pretty much similar:

Water roux:
20g plain flour
100g water

Dough:
350g bread flour
160g milk
5g dry instant yeast
30g sugar
5g salt
35g butter.

I had some custard filling and sugar crust already made from last batch of pineapple buns (they don't have pineapples in them but the crust was scored to look like pineapple skins?)

I made the water roux as per instruction, made the dough and proof the dough as normally it would happen for us and then shaped the buns with fillings and covered with the crust:

They proof alright,

I didn't watch the oven and I must admit I was 3 minutes too late...

But nothing too exciting about the result... so I'm not really sure water roux is the way to go or not for the next batch of bread, whatever it is.