If the refund is just for housing then the amount on the 1098-T won’t be affected but your 1099-Q for 2020 will show total withdrawals that are higher than your actual expenses. It may make your life more difficult when completing your tax return if that pulls in data from the 1099-Q automatically.
Interestingly if the refund is counted as a new after tax contribution then it will raise the effective tax basis of your account (ie a lower percentage of future distributions will be earnings). That is modestly beneficial if money is eventually left over and is taken as a taxable withdrawal.
As an example, say you had $50K in there which was half contributions and half earnings and had withdrawn $10K for this semester. If you put back $5K then you will now have $25K contributions and $20K of earnings and future withdrawals will be 55.6% from contributions and 44.4% from earnings. Any money left over will be in this proportion also. Whereas if you’d kept the original amount in your checking account the 529 balance would still be 50% earnings.