I couldn't find anything for this season, but Sam Hauser dropped the most points by a player off the bench in the NBA Finals, with 41 points.

Interpreted as:

most bench points by a player this final

	NAME	PTS	SERIES	GP	MPG	PPG	RPG	APG	SPG	BPG	FGM	FGA	FG%	3PM	3PA	3P%	FTM	FTA	FT%	TS%	OREB	DREB	TPG	MIN	REB	AST	STL	BLK	TOV	PF	+/-
1	Sam Hauser S. Hauser	41	NBA Finals	5	15.5	8.2	3.0	0.6	0.2	0.0	2.8	5.4	51.9	2.2	4.6	47.8	0.4	0.4	100.0	73.5	1.0	2.0	0.0	78	15	3	1	0	0	7	+17
2	Kristaps Porziņģis K. Porziņģis	37	NBA Finals	3	20.0	12.3	3.7	0.3	0.0	1.7	4.7	8.0	58.3	0.7	3.0	22.2	2.3	2.7	87.5	67.2	0.0	3.7	0.3	60	11	1	0	5	1	5	+33
3	Dereck Lively II D. Lively II	28	NBA Finals	5	22.8	5.6	8.2	0.4	0.8	0.2	2.4	3.4	70.6	0.2	0.2	100.0	0.6	1.4	42.9	69.7	3.2	5.0	1.0	114	41	2	4	1	5	11	-10
4	Josh Green J. Green	27	NBA Finals	5	19.4	5.4	2.8	0.6	0.4	0.0	1.8	4.0	45.0	1.2	2.2	54.5	0.6	1.2	50.0	59.6	1.0	1.8	0.0	97	14	3	2	0	0	5	-4
5	Jaden Hardy J. Hardy	21	NBA Finals	5	6.5	4.2	1.2	1.0	0.0	0.0	1.4	3.2	43.8	0.4	1.0	40.0	1.0	1.2	83.3	56.3	0.2	1.0	0.2	33	6	5	0	0	1	3	-3
6	Dante Exum D. Exum	19	NBA Finals	5	8.2	3.8	1.0	0.4	0.2	0.0	1.4	2.0	70.0	0.8	1.2	66.7	0.2	0.4	50.0	87.3	0.0	1.0	0.6	41	5	2	1	0	3	2	+16
7	Payton Pritchard P. Pritchard	17	NBA Finals	5	12.4	3.4	1.4	1.6	0.2	0.0	1.4	5.6	25.0	0.6	3.2	18.8	0.0	0.0		30.4	0.4	1.0	0.6	62	7	8	1	0	3	6	+2
8	Tim Hardaway Jr. T. Hardaway Jr.	15	NBA Finals	4	11.9	3.8	1.5	0.3	0.3	0.0	1.3	3.8	33.3	1.3	3.0	41.7	0.0	0.0		50.0	0.0	1.5	0.0	48	6	1	1	0	0	3	-9
9	Maxi Kleber M. Kleber	9	NBA Finals	5	15.9	1.8	1.4	0.6	0.2	0.2	0.6	2.4	25.0	0.2	1.2	16.7	0.4	0.4	100.0	34.9	0.2	1.2	0.2	80	7	3	1	1	1	8	-14
10	Oshae Brissett O. Brissett	7	NBA Finals	3	6.2	2.3	1.0	0.0	0.0	0.3	0.7	1.3	50.0	0.3	0.3	100.0	0.7	0.7	100.0	71.7	0.3	0.7	0.0	19	3	0	0	1	0	0	-3
11	Xavier Tillman Sr. X. Tillman Sr.	6	NBA Finals	2	9.3	3.0	2.5	0.5	0.0	1.0	1.0	1.5	66.7	0.5	0.5	100.0	0.5	0.5	100.0	87.2	1.0	1.5	0.5	19	5	1	0	2	1	3	-4
12	Svi Mykhailiuk S. Mykhailiuk	5	NBA Finals	3	4.4	1.7	0.7	0.0	0.0	0.0	0.7	2.7	25.0	0.3	1.7	20.0	0.0	0.0		31.3	0.0	0.7	0.0	13	2	0	0	0	0	0	-10
13	Markieff Morris M. Morris	3	NBA Finals	1	12.0	3.0	4.0	0.0	0.0	0.0	1.0	5.0	20.0	1.0	3.0	33.3	0.0	0.0		30.0	0.0	4.0	1.0	12	4	0	0	0	1	1	+6
14	Neemias Queta N. Queta	2	NBA Finals	1	5.4	2.0	0.0	0.0	0.0	1.0	1.0	1.0	100.0	0.0	0.0		0.0	0.0		100.0	0.0	0.0	0.0	5	0	0	0	1	0	0	+7
15	A.J. Lawson	2	NBA Finals	2	5.3	1.0	0.0	0.0	0.0	0.0	0.5	1.0	50.0	0.0	0.0		0.0	0.0		50.0	0.0	0.0	0.0	11	0	0	0	0	0	0	+2
16	Luke Kornet L. Kornet	2	NBA Finals	3	5.1	0.7	0.7	0.7	0.3	0.0	0.3	0.7	50.0	0.0	0.0		0.0	0.0		50.0	0.7	0.0	0.0	15	2	2	1	0	0	2	-14