Yes those two Australian Open matches were also very important. However their US Open matches were more important, as both players simply cared a lot more about the US Open than the Australian Open, which was understandable given that they were both American. Had Agassi lost to Sampras at the Australian Open, it's difficult to imagine him taking it anywhere as badly as he took that 1995 US Open defeat.
Still I agree that the 2000 Aussie Open semi was a huge win for Agassi. Sampras was the pre-match favourite given how he had owned Agassi in 1999 and had the upper hand in most of their big matches. However this time Agassi battled away and withstood everything that Sampras threw at him, and came out on top. Sampras was 2 points away from a 4 set win as well, and had benefited from the faster conditions that year.
In 1995, Agassi hadn't dropped a single set until the final, and Sampras was physically and emotionally drained following the whole Tim Gullickson turmoil and the battles against Courier and Chang. All things considered he did very well just to reach that final, and Agassi was the clear favourite there.
It's interesting that Sampras won both his Australian Open titles without Agassi in the draw (although it's difficult to imagine the Agassi of 1997 being a threat to Sampras or any of the top players), while Agassi benefited from Sampras injuries to win both of his US Open titles.