`RewindBlockIndex` was made to allow nodes upgrading to new consensus rules post-segwit fork to 
download new consensus data (i.e witnesses) without having to go through a whole IBD. It has been pointed than now really few pre-segwit nodes care to upgrade and that this logic may be irrelevant.

See https://github.com/bitcoin/bitcoin/pull/17737#discussion_r358514335 in review  of #17737 for more context pointers.
} catch (const std::exception& e) {
                LogPrintf("%s\n", e.what());
                strLoadError = _("Error opening block database");
                failed_verification = true;
                break;
            }
            if (!failed_verification) {
                fLoaded = true;
                LogPrintf(" block index %15dms\n", GetTimeMillis() - load_block_index_start_time);
            }
        } while(false);
        if (!fLoaded && !ShutdownRequested()) {
            
            if (!fReset) {
                bool fRet = uiInterface.ThreadSafeQuestion(
                    strLoadError + Untranslated(".\n\n") + _("Do you want to rebuild the block database now?"),
                    strLoadError.original + ".\nPlease restart with -reindex or -reindex-chainstate to recover.",
                    "", CClientUIInterface::MSG_ERROR | CClientUIInterface::BTN_ABORT);
                if (fRet) {
                    fReindex = true;
                    AbortShutdown();
                } else {
                    LogPrintf("Aborted block database rebuild. Exiting.\n");
                    return false;
                }
            } else {
                return InitError(strLoadError);
            }
        }
    }