You can believe what you want to believe. If Valve was Japanese or Chinese maybe I'll buy the "don't want to sell" angle due to "economic national security concerns" aka the politics angle (which is absolutely a real thing) but they're an American company, in Washington state (home of MS), operating on the Windows platform for the overwhelming majority of their business, founded by ex-MS employees and who, when pushed to pick a side in the console wars, always picked the MS side (and does so today). For that, and the many other reasons that I've stated in my previous posts I'm fully of the opposite opinion.
It's a legitimate seed of doubt and it should hang overhead for anyone that cares about their long-term platform investment in this new era of consolidation. Again, no western dev house and software distribution platform is safe - much less on PC, Microsoft's home turf, of all places. The funniest thing is seeing PCMR Valve fanboys believe they're safe with Gabe and that all these shenanigans affect evil Sony only - the eternal enemy on consoles - while PC gets a free ride as if there is some imaginary block preventing Microsoft from gobbling up Steam. There is not. When you get away with acquiring the biggest publisher on the planet, as well as a private company like Valve in Bethesda, another publisher, back-2-back and the whole system of check and balances crumbles at your corrupting feet no one, specially one as attractive like Valve, is safe.
One of the many reasons monopolies and duopolies are bad. So yeah the sheep can cheer Epic's Game Store being insignificant, while throwing all your money and loyalty at Steam like faithful, mindless servants - ok. Will Valve be as loyal to you? It's a for profit corp - always press X for doubt. "Loyalty" has a price - it's just a slider to the right, in this case, measured in billions of dollars. The real question is how important Microsoft believes Valve consumer base on PC is to their long-term strategic plans - that has a dollar value like everything else. In layman - your Steam library being for sale.