Not exactly. I didn't spell out the details in my statement. So, yes, there are many companies that make better parts for the bimmer than what BMW offers, or even make things that BMW doesn't offer.
I've yet to get my hands on any 3rd party lens that measures up to the Nikon or Canon equivalent. Believe me, I've tried. I have thousands of dollars of Nikon glass, and I'd love to be able to get what I want from a $200 lens instead of a $1400 lens. Sadly, I've had no such luck. Sometimes they come close, but every review I've read, and every time I've tried them myself, they never measure up. Some reviews I've read say "for the money" they're close, but no, they don't measure up, period. The 3rd party stuff is also worthless at re-sale. The Canon and Nikon lenses hold their value very well, so in the long run, they cost less to own and use.
1999 e46 328i Ti Silver / Black[retired]
2007 e90 335xi Jet Black / Black[retired]
2011 e70 X5 35d Vermillion Red / Cinnamon
2011 e92 M3 LeMans / Fox Red extended