Never used indiabonds, so not exactly sure what their offering are, but in my view, minimum amount to invest also depend on what type of issuance was done for original bonds.
As such SEBI has come up with recent circular, mandating that for privately placed debt instruments, minimum face value has to be Rs. 10 lakhs
And since most of these platform are dealing in privately placed instruments, I think going forward, everyone will have to move to min 10 lakh investment (unless bonds were issued as part of public issue, in which case face value can be low)