if it is same is in onroad ESCs like RS pro than timing boost will increase timing after some time on full throttle to further increase top speed at straights. It is usefull if straights are very long (like 2+seconds) so after like 1 second ESC will increase timing of the motor increasing its RPMs (and of course heat)
Radek
V4 D8 - RX8, XERUN 4168SD
F1-09 - Tekin RS Pro, 17.5t Redline, 2S LiPo
Sakura Zero S - LRP, Saturn 20T, 2S LiPo
*EX-10 Eurus*