So this seems very clear to me. While there appears to be two separate documents, they say the same thing.
At the expiry of the fixed rate period, your loan will revert to the IIB Homeloans Renewal rate...[which is] a variable rate and may be varied by the lender from time to time in line with the general market conditions.
At the expiry of the fixed rate period, the Lenders prevailing variable rate will apply.
The handbook explains what a variable rate is which is what the common understanding of a variable rate is. It also explains that is is different from a fixed rate and from a tracker rate.
The AIB and ptsb contracts were very different. "At the end of the fixed rate period, you will be offered a choice of fixed, variable or tracker at the then prevailing rates"
If you have that contract and that handbook, you would have a huge job persuading a court or the Ombudsman that you were entitled to a tracker when the fixed rate expired. Certainly worth going to the Ombudsman as it costs you nothing, but I don't think it's the worth the risk of a High Court case.
Again I will stress that I am referring to the above wording. Someone may get an entitlement to a tracker through a flyer or some other communication. But that is a very separate issue.