In answer to your question of course upon death siblings should be treat equally. Most parents likely word the will to be split equally between the siblings and if one sibling happened to pass away, their share would be split between any children they may have. This is fair.
The other thread was about gifting money while living with the intention of the sister gaining upon the parents death. Most people are aware that circumstance can change and I don't believe in that instance the OP should have been responsible for her father's decision.
I was on the side of the original poster on the inheritance thread. Her dad chose to gift her children a private education while still living on the premise that the sibling inherited the same upon his death.
Unfortunately due to unexpected reasons there was no money left in the estate leaving the sibling with nothing. What if the OP did not have 150k savings, what would be expected then?
Personally I would be happy that my parent was able to fulfil their own dreams while living and if that meant me being at a disadvantage, I would be happy for them.
This said, I personally would treat my own children the same. If I gifted 1 child's household 100k, I would do the same for the other at the same time and it would be their choice how to use it.
It may sound hypocritical but I could not deny the joy it would have brought my parents to do something that meant so much to them while still living.