Think the noise about Smith in the 4th has been about it being matchwinning rather than the average. When he went big in the 4th, RSA always won, but it is a combo of RSA style of attrional cricket and being generally pretty strong in his era that enabled it.Much is made about Smith in the 4th innings but in the last 50 years these are the 4th innings averages:
Boycott 61.77!!
Greenidge 54.92!
Gavaskar 52.50
Smith 51.68
Hayden 49.50
Gooch 47.47
Interesting Sehwag (who often went nuts early in tests) 32.17
Sehwag is interesting. i have heard him described on CW as possibly the best player pf spin ever (no idea tbh, only ever watched him against utterly janky rsa spinners). but that is a low 4th average considering thanks prause he gets