There are really 2 very different answers to "locked: Y/N?".
1. is the position of the piston when the spark kernel begins to expand away from the ignition source. In addition to compensating for the time in milliseconds balancing piston accelerating away from TDC to advancing flame front (which dies out after perhaps 3,000 RPM), the remainder is based on the cylinder pressure (combustion, not CCP), A:F mixture, droplet size, fuel chemical characteristics, VE, and how many intermediate stages of combustion take place (before final conversion to water and CO2), and boost.
2. is how many of these are relevant to a maximum effort engine that only needs to start, idle (more or less), stage, launch and WOT. Sometimes this answer is so close to "only 1" that the exceptions are more trouble than they're worth. I've never seen an engine with idle quality exactly the same with 15° and 40° spark; the idle speed may not differ significantly but the spark position can be selected by choosing the LOUDEST position.