If the market leader has 90% market share and they grow to 95%, they have grown a lot less than you relatively (so the minor player can claim they have grown the most) but they now own a bigger piece of the pie than they used to.
This is why you should always be skeptical of anyone who uses relative numbers (growth) instead of absolute ones: the reality is probably that they have lost market share.
Which is what we have seen Apple do compared to Android these past three years.
You will notice that the early keynotes right after the iPhone and iPad came out were showing absolute numbers in shipments and dollars, and now, they just stick to percents and vague claims ("We're growing the fastest").
For example, below appears to be the report Cook used for his "+14% vs -0.4%" slide, which at best, is very misleading.
"In the worldwide mobile phone market (inclusive of smartphones), vendors shipped 464.6 million units, down -0.4% from the 466.3 million units shipped 2Q14.[1]"
Truth is, the smartphone market actually GREW by 11.6% (Q2 2014:302.1m => Q2 2015:337.2m).
1980: Apple has 10% of a 100,000,000-phone market. We could call this a gap of 90,000,000.
1981: Apple has 15% of a 200,000,000-phone market. We could call this a gap of 170,000,000. What happened was that while Apple's market share grew, it grew much slower than the market itself.
I guess you might want to look at the world that way; for example, if you wanted to know how difficult it would be to convince the entire market to switch to your product. But I tend to agree that market share would seem to be more useful for most purposes.