Big3 in their 30s are 20-1 against non-ATGs in Slam finals - Could it ever happen if they were not peak?

[junkieballer]

Big3 in their 30s played these 21 Slam finals against non-ATGs and won 20 of them:

WI12 Federer defeats Murray
RG17 Nadal d. Wawrinka
WI17 Federer d. Cilic
UO17 Nadal d. Anderson
AO18 Federer d. Cilic
RG18 Nadal d. Thiem
WI18 Djokovic d. Anderson
UO18 Djokovic d. Del Potro
RG19 Nadal d. Thiem
UO19 Nadal d. Medvedev
AO20 Djokovic d. Thiem
AO21 Djokovic d. Medvedev
RG21 Djokovic d. Tsitsipas
WI21 Djokovic d. Berrettini
UO21 Medvedev d. Djokovic
AO22 Djokovic d. Medvedev
RG22 Nadal d. Ruud
WI22 Djokovic d. Kyrgios
AO23 Djokovic d. Tsitsipas
RG23 Djokovic d. Ruud
UO23 Djokovic d. Medvedev

This seems like a list of quite good players.

My question is: could Big3 be 20-1 in Slam finals against these non-ATGs without playing their best tennis?

 

[junkieballer]

In their 20s Big3 were only 21-6 against non-ATGs in Slam finals.

In their 20s = 21-6 (77.8%)
In their 30s = 20-1 (95.2%)