Well I tried it with my usual method of making custard and there was no difference.
I heated up 250ml of original Almond milk with 1/2 tsp vanilla paste and roughly 20g jaggery in a saucepan. Brought it to the point of boiling and took it off the heat. Meanwhile I had mixed 2 tablespoons of rice flour with the single whole egg cracked into a small bowl. I didn't whisk the egg first, saw no point. I used the small whisk to beat the egg and four together thoroughly. Then I added a small amount of the milk mixture beating well. Added some more, beat again and then the rest. Returned to the pan, brought back to the boil whilst whisking all the time and then simmered for a few minutes before serving. No issues with egg white looking at me, no issues with scrambled egg etc. I honestly couldn't tell the difference. So I will use whole egg in future.