BUG #18600: Getting wait_type_event as IPC:BTreePage for count queries

The following bug has been logged on the website:

Bug reference: 18600
Logged by: Aditya Singh
Email address: aditya(dot)singh(at)lji(dot)io
PostgreSQL version: 13.11
Operating system: macOS
Description:

Table1:
Structure:
CREATE TABLE "femsa"."activities_bit" (
"id" int4 NOT NULL DEFAULT
nextval('femsa.activities_bit_copy_id_seq'::regclass),
"created_ts" timestamptz,
"member_id" varchar(40),
"bit_reference" varchar(32),
"header" jsonb,
"payment_details" jsonb,
PRIMARY_KEY("id")
}

Table 2:
Structure:
CREATE TABLE "femsa"."activities_bit" (
"id" int8 NOT NULL DEFAULT
nextval('femsa.activities_bit_copy_id_seq'::regclass),
"created_ts" timestamptz,
"member_id" varchar(40),
"bit_reference" varchar(32),
"header" jsonb,
"payment_details" jsonb,
PRIMARY_KEY("id")
}

The only difference between the two is the data type of the id sequence
(int, bigint).

SELECT COUNT(*) FROM {table_name} WHERE id > 0;
When I try to run the above query, I get the result for Table 1, but the
query on Table 2 goes into wait_type_event IPC:BtreePage.

Why this IPC:BtreePage is coming for Table2 when both tables have similar
structure, data and Indexes?