1)the APB uses massive memory-I/O accesses.what is that massive memory-I/O accesses?
Personally I would ignore that article as it makes little sense. I have absolutely no idea what the author means with the text you are questioning, so as it isn't anything produced by ARM you would really need at ask the author what they meant.
All the article really tells me is what the letters AHB and APB stand for, that AHB is pipelined and APB is not, that AHB is higher performance and supports more complex slaves like memories and APB is a lot simpler and is designed for simple lower bandwidth peripherals... all of which you'd get from reading the AHB and APB spec introductions, so not sure what the article is really trying to achieve.
If I put "massive memory-I/O" into google, it suggests "Memory-Mapped IO"
But, as Colin Campbell says, you'd really have to ask the author of that article what he meant by it.
This shows the importance of giving a link so that we can see context!