GNU date: truncate provided date-time and set provided hours

You can always specify the time as part of the output format:

$ date -d @1595413447 '%a %b %e 10:05:00    %Y'
Wed Jul 22 10:05:00    2020

Or more portably (avoiding the GNU date dependency) in the ksh93 shell:

$ printf '%(%a %b %e 10:05:00    %Y)Tn' '#1595413447'
Wed Jul 22 10:05:00    2020

Though ksh93 also supports:

$ printf '%(%a %b %e %T    %Y)Tn' '#1595413447 10:05'
Wed Jul 22 10:05:00    2020

Or in the zsh shell:

$ zmodload zsh/datetime
$ strftime '%a %b %e 10:05:00    %Y' 1595413447
Wed Jul 22 10:05:00    2020

Or in the bash shell (bash copied ksh93's printf %T for formatting but not for date parsing):

$ printf '%(%a %b %e 10:05:00    %Y)Tn' 1595413447
Wed Jul 22 10:05:00    2020

GNU date doesn't allow any additional specifications to a timestamp.

From the date info documentation:

If you precede a number with ‘@’, it represents an internal timestamp as a count of seconds. The number can contain an internal decimal point (either ‘.’ or ‘,’); any excess precision not supported by the internal representation is truncated toward minus infinity. Such a number cannot be combined with any other date item, as it specifies a complete timestamp.

^{(emphasis mine)}

I'm afraid you need two invocations, such as

date -d "$(date -d @1595413447 +'%F 10:05')"