Why tiger(Modern Compiler Implementation) use `fundecs` in chapter 4 instead of `fundec`?

Question

I'm following the tiger book to write a compiler.

In chapter 3, based on the github's code and my understanding, I filled in the following rules for the dec:

decs:
    %empty
    | decs dec
;

dec:
    tydec
    | vardec
    | fundec
;

tydec: 
    TYPE ID '=' ty
;

vardec:
    VAR ID ASSIGN exp
    | VAR ID ':' ID ASSIGN exp
;

fundec:
    FUNCTION ID '(' tyfields ')' '=' exp
    | FUNCTION ID '(' tyfields ')' ':' ID '=' exp

However, in chap 4, the book provided the following functions for ast:

A_fundecList A_FundecList(A_fundec head, A_fundecList tail);
A_nametyList A_NametyList(A_namety head, A_nametyList tail);

Which made the most of code I found adjust the decs token as follow

decs:
    %empty
    | decs dec
;

dec:
    tydecs
    | vardec
    | fundecs
;

tydecs:
    tydec
    | tydec tydecs

tydec: 
    TYPE ID '=' ty
;

vardec:
    VAR ID ASSIGN exp
    | VAR ID ':' ID ASSIGN exp
;

fundecs: 
    fundec
    | fundec fundecs    {$$ = A_FundecList($1, $2);}
;

fundec:
    FUNCTION ID '(' tyfields ')' '=' exp
    | FUNCTION ID '(' tyfields ')' ':' ID '=' exp

The list token fundecs and tydecs were added into the production rule.

I do not understand why doing that, since this will obviously create conflict. Because decs is a list can contain fundecs and tydecs. So a list of fundecs, for example, can be reduced to either a list of decs or a list of fundecs.

Thus I would like to ask why doing this, what is the reason of adding conflict grammar for the parser??

Thanks a lot!!!