Hi Applesead, I think you're right, its a strategic play on the future use of the Eth.
In addition to everything Shadow, Aigur, JFry4, and others have said, (protecting against USD deterioration, stablecoin risk, having a basket of decentralized unhackable assets)... including 5% Eth in the treasury without minting is a long-term play. There's no need to mint more Ohm off of Eth in the short-term, the current runway is considerable and has been growing continuously through partnerships and bonding.
Some of the runway extension also comes from forced buyers and sellers during periods of volatility, when the treasury protocol gains Dai by picking up spreads. This was even visible during the last drawdown when APY shifted from 15k to 16k for one epoch.
Also, it's useful as insurance against the unlikely event of Olympus DAO price decreasing considerably, 90% for example, having more Eth in the treasury acts as a strong incentive for buyers of last resort. Whoever buys the dip of the dip knows their will have a claim on whatever Eth is in the treasury if things go really south.
If for some reason something very bad were to happen to stablecoins, this wouldn't necessarily impair Eth, so that helps as a hedge. Especially since many people would flock from stables to the nearest bankrupcy proof asset.
Finally, growing a 5% Eth position will allow Olympus to participate in Eth 2.0. There will be benefits in terms of both passive income, MEV capture (I'm sure others can explain this better than me), and having a voice in Ethereum governance by possessing a staking pool.
Even if over time we successfully migrate much of Ohm governance to code, it will be very important to have influence in Eth governance since Ohm is built on Eth and currently does not have any other safe harbors.
Cheers,
Fulano (Α, Ω)