One may call it tactic, but, the way you have described it, it does not look far too unfair. The digits do overlap, indeed, and given a range does not necessarily imply you are granted a median (or an upper) value.
We can't tell for sure if it's tactic or not. The only thing, likewise everywhere, is a rule, offer as few as you can and demand as much as you can.
The other consideration I would like to draw your attention to, is your performance.
One of the primary goals of temp-to-hire status is discovering how an applicant performs on their job.
The meaning of salary range is that your final offer may vary depending on how you performed. It's your right to fight for a better offer, and one of the most effective ways is improving your results.
If I were you, I would come up with the following question:
Talking to Mr. John Agent, we spoke about a different range, 100-115 units. My goal is having 110 units. Since you have a different range, does it mean I have performed worse than you expected? If so, I would like to improve my results so that you were glad to offer me 110.
I have two months before final term, it's plenty of time. Are there any ways I can improve it?
Can you suggest me some books to improve my knowledge?
During these 2 months, may I ask for tasks that require greater proficiency?
Note, you are not asking for more just because you want it. Also, you don't put your boss or an agent into an awkward situation of "conflicting information". Instead, you demonstrate your positive attitude, willingness to work and and accomplish greater results, ability and desire to learn, and so on.