This is a common practice when a certain percentage of Total Supply is distributed among the project team. And as I know, these coins will be subject to a lock for 4 years. But the 26.94% you write about is the total number of coins that will be distributed for the Offchain Labs organization, which includes team members.
Yes it's a common practice but it's completely wrong. It's basically premined more than quarter of coins, nobody would like to touch a coin with too much premine.
Crypto environment have to be evolved and don't let these things happen.
The Arbitrum does not have a premain. Total Supply ARB in the amount of 10,000,000,000 coins is fully printed and in accordance with the roadmap, all these coins have a lock, with the exception of coins allocated for airdrop. The next unlocked ARB coins will appear on the market in 1 year.