Seniors penalized for using internet

Some time ago I visited Falls Creek. Before the visit I examined the resort web page and found information, that purchasing resort entry on internet I can get $3 discount per day. Apart from saving $3 (full price is $45) I took into consideration fact, that buying on internet I save time spent on the gate so I chose this option.
Reading Terms and Condition page...

I noticed a separate paragraph for over 65's - it said that they are eligible for 10% discount for season tickets. Why not on daily tickets? Anyway, rules are rules, I purchased ticket for 2 days.

Couple of days later I arrived at the gate and noticed information, that over 65's are entitled to 10% discount also on daily tickets - that means $4.50 instead of $3..
- Why it is not mentioned on the web page - I asked.
- It was technically difficult to process discounted daily tickets for seniors - was the answer.

I understand, that we are only in 14th year of 21st century and some complex problems have still to wait for solutions, but why the Terms and Conditions page does not contain information, that seniors buying daily pass are eligible for 10% discount only if they buy tickets at the gate?

The person at the gate was very polite and advised me to go to the resort office with all my receipts and request a  refund, but the amount was not worth the effort.

But my question still remains unanswered - why the Terms and Conditions page does not contain information, that seniors buying daily pass are eligible for 10% discount only of they buy tickets at the gate?
I consider this as very unfair and arrogant treatment.