Electrically, delta and Y motors are the same for both use as a rotary phase converter, and as a motor when run on single phase.
However: thermally, they are not the same. The Y motor spreads the heat out over 2/3rds of the stator core when run on single phase.
The delta motor spreads 75% of the heat out across one third of the stator core, the other 25% across the other 2/3rds of the stator core. so they have to be derated more.
So anyhow, regarding a 6 pole motor as an idler I would go ahead and try it, but my estimate is that it will perform as an idler in a similar manner as a 7.5 hp 1700 or 3400 rpm motor.
The reason why is because 6 pole motors typically have 10-20% more leakage inductance due to some fundamental geometry problems.
However, this also depends on the length to width ratio of the coils. your motor only draws 27 amps at 10hp which is not bad at all. I have a 5hp motor of 91% efficiency and 83% power factor that draws 12.3 amps at 230volts. yours is only 10% higher, some of which is accounted for by the 5% difference between 220 and 230volts.
so basically your 6 pole motor assuming the same efficiency as mine, is probably running at around 75% power factor.
the higher power factor makes adjusting the voltage with capacitors easier, but the generated leg is not as stiff.
I have an 8 pole motor and it runs at a power factor of just 0.6, and would be somewhat useless as an idler.