The USBC rule that was implemented when a certain youth bowler fraudulently claimed he bowled multiple 900-series deals only with unopposed pre- and post-bowling. If you bowl during your regularly scheduled league time, it does not matter whether you have an opponent bowling with you or not. If there are an odd number of teams and you're bowling the vacancy team that night, and you bowl at your usual league time, those scores count for every conceivable award or payout.
If you are bowling an actual team (not a ghost team or vacancy team) and you pre- or post-bowl with them, those scores count for every possible award category you could think of.
If you pre- or post-bowl by yourself or with only your team present then your scores are not eligible for the 300 game, 11-in-a-row, 800- or 900-series, no national high game or series awards. If you don't have a league rule about being ineligible for local awards or league awards, then they are eligible.
If there is another team present, no matter when you bowl, they're eligible.
SH