What is a consulting firm?
Perhaps IT shop is more accurate.
Strategic alliances brings up a good way to broaden your skills and offerings. In the gogo days of early 90s there was so much network installation and server management work that we subcontracted out most cable installations and phone systems. When things slowed down we brought it in house as we were used to offering it, knew the salient issues and obtained the skills. Likewise with internet hosting and email hosting. Likewise with programming and development. Again as other profit centers began to slow down we picked up the opportunities in break/fix and opened retail stores. That was some of the best profits we made in 20 years. As laptop computer sales approached workstations we saw the writing on the wall to keep those profits we needed to adapt. So we made a special effort to get certified by Toshiba to do that. About four or five years ago the same thing happened with Iphones, ipads and androids. If you didn't keep up you just saw your market share decline.
We been doing this since Novel and Banyan vines. If you didn't have the ability and nature to quickly learn new things you just do not survive. You cannot be all things to all people but you definitely must be very much aware of where your bread is buttered and what is happening to that service and where your next loaf is going to be buttered. Adapt and survive.
I think the author could have said it better by saying "stick to what you know" But "always be expanding what you know and where your customers are coming from."